In Republican hands for 28 years but now up for grabs, a suburban Missouri congressional district hugging St. Louis has become a lab for what each party considers one of its most lethal political weapons.

TV ads by GOP Rep. Ann Wagner show protesters stomping a police car as the narrator accuses Democratic challenger Jill Schupp of support from “radical defund the police organizations.” A Schupp spot says Wagner voted “against people with preexisting conditions during COVID.” The coronavirus causes COVID-19.

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FILE - In this Sept. 5, 2020 file photo, police use chemical irritants and crowd control munitions to disperse protesters during a demonstration in Portland, Ore. In the campaign for House control, some districts are seeing a fight between Democrats saying they'll protect voters from Republicans willing to take their health coverage away, while GOP candidates are raising specters of rioters imperiling neighborhoods if Democrats win. (AP PhotoNoah Berger, File)

In Republican hands for 28 years but now up for grabs, a suburban Missouri congressional district hugging St. Louis has become a lab for what each party considers one of its most lethal political weapons.

FILE - In this Sept. 7, 2020 file photo, armed right-wing protesters in support of President Donald Trump stand in front of the Oregon State Capitol in Salem, Ore. In the campaign for House control, some districts are seeing a fight between Democrats saying they'll protect voters from Republicans willing to take their health coverage away, while GOP candidates are raising specters of rioters imperiling neighborhoods if Democrats win. (AP PhotoAndrew Selsky, File)

Scores of suburban districts are back in play in the GOP's long-shot attempt to win House control in November's election. Democrats who used health care to capture the majority in 2018 are emphasizing it anew, saying they'll shield voters from Republicans trying to tear coverage away during a pandemic.

FILE - In this March 26, 2019 file photo, Speaker of the House Nancy Pelosi, D-Calif., joined at left by Energy and Commerce Committee Chair Frank Pallone, D-N.J., speaks at an event to announce legislation to lower health care costs and protect people with pre-existing medical conditions, at the Capitol in Washington. In the campaign for House control, some districts are seeing a fight between Democrats saying they'll protect voters from Republicans willing to take their health coverage away, while GOP candidates are raising specters of rioters imperiling neighborhoods if Democrats win. (AP PhotoJ. Scott Applewhite, File)

“If I don’t win, America’s Suburbs will be OVERRUN with Low Income Projects, Anarchists, Agitators, Looters and, of course, `Friendly Protesters,'” he tweeted recently.

FILE - In this March 28, 2019, file photo, President Donald Trump speaks at a campaign rally in Grand Rapids, Mich. In the campaign for House control, some districts are seeing a fight between Democrats saying they'll protect voters from Republicans willing to take their health coverage away, while GOP candidates are raising specters of rioters imperiling neighborhoods if Democrats win. (AP PhotoManuel Balce Ceneta, File)

Each party says their messaging is poll-tested and will work.

A Biden for President sign in a lawn of suburban Dublin, Ohio, on Friday, Sept. 18, 2020. In the campaign for House control, some districts are seeing a fight between Democrats saying they'll protect voters from Republicans willing to take their health coverage away, while GOP candidates are raising specters of rioters imperiling neighborhoods if Democrats win. (AP PhotoJulie Carr Smyth)

So far, public polling offers scant evidence that the GOP's law and order arguments have taken hold.

Signs in support of President Donald Trump and other Republican candidates on a lawn of a suburban Dublin, Ohio, home on Friday, Sept. 18, 2020. (AP PhotoJulie Carr Smyth)

Republicans say they've detected growing support on the issue since last month's violence in Kenosha, Wisconsin, after police shot a Black man. This summer's racial justice protests have been largely peaceful, but images of violent ones have received widespread attention.

FILE - In this June 5, 2018, file photo Orange County Supervisor Michelle Steel smiles as she visits Rep. Dana Rohrabacher's election night party in Costa Mesa, Calif. Republican challenger Michelle Steel has talked about taxes, while Democratic Rep. Harley Rouda has focused on health care and prescription drug costs. In the campaign for House control, some districts are seeing a fight between Democrats saying they'll protect voters from Republicans willing to take their health coverage away, while GOP candidates are raising specters of rioters imperiling neighborhoods if Democrats win. (Jeff GritchenThe Orange County Register via AP, File)

“I think Democrats are vulnerable to it," said Sam Geduldig, who advised former House Speaker John Boehner, R-Ohio. “But the harder you go on it, the more it turns off some of those wealthy suburban voters in some districts we need."

The pattern is similar outside Philadelphia, where GOP Rep. Brian Fitzpatrick accuses Democratic challenger Christina Finelo of supporting police defunding. Finelo's first ad says Fitzpatrick's backed ending coverage for people with preexisting conditions. Each contests the other's charge.

FILE - In this Sept. 5, 2020 file photo, police use chemical irritants and crowd control munitions to disperse protesters during a demonstration in Portland, Ore. In the campaign for House control, some districts are seeing a fight between Democrats saying they'll protect voters from Republicans willing to take their health coverage away, while GOP candidates are raising specters of rioters imperiling neighborhoods if Democrats win. (AP PhotoNoah Berger, File)

FILE - In this Sept. 5, 2020 file photo, police use chemical irritants and crowd control munitions to disperse protesters during a demonstration in Portland, Ore. In the campaign for House control, some districts are seeing a fight between Democrats saying they'll protect voters from Republicans willing to take their health coverage away, while GOP candidates are raising specters of rioters imperiling neighborhoods if Democrats win. (AP PhotoNoah Berger, File)

Scores of suburban districts are back in play in the GOP's long-shot attempt to win House control in November's election. Democrats who used health care to capture the majority in 2018 are emphasizing it anew, saying they'll shield voters from Republicans trying to tear coverage away during a pandemic.

“This is as current an issue as can possibly be,” said Leslie Dach, who heads the Democratic-backed Protect Our Care Coalition.

In some races, Republicans are talking up lawlessness to try stemming defections of educated, moderate suburban voters from the GOP, spurred by aversion to President Donald Trump. But even where Republican candidates promote themes such as rebuilding the economy, Trump’s blunt-force ads and his tweets on law and order have kept it in the forefront.

FILE - In this Sept. 7, 2020 file photo, armed right-wing protesters in support of President Donald Trump stand in front of the Oregon State Capitol in Salem, Ore. In the campaign for House control, some districts are seeing a fight between Democrats saying they'll protect voters from Republicans willing to take their health coverage away, while GOP candidates are raising specters of rioters imperiling neighborhoods if Democrats win. (AP PhotoAndrew Selsky, File)

FILE - In this Sept. 7, 2020 file photo, armed right-wing protesters in support of President Donald Trump stand in front of the Oregon State Capitol in Salem, Ore. In the campaign for House control, some districts are seeing a fight between Democrats saying they'll protect voters from Republicans willing to take their health coverage away, while GOP candidates are raising specters of rioters imperiling neighborhoods if Democrats win. (AP PhotoAndrew Selsky, File)

“If I don’t win, America’s Suburbs will be OVERRUN with Low Income Projects, Anarchists, Agitators, Looters and, of course, `Friendly Protesters,'” he tweeted recently.

Wagner has voted for bills that would have ended the coverage that former President Barack Obama’s health care law guarantees people with preexisting conditions. She’s introduced bills to protect such coverage, her campaign says.

Schupp has said she opposes defunding police, a far-left call to restructure and even cut police agencies that many Democrats reject. She's been backed by Indivisible, a progressive group that supports the proposal.

FILE - In this March 26, 2019 file photo, Speaker of the House Nancy Pelosi, D-Calif., joined at left by Energy and Commerce Committee Chair Frank Pallone, D-N.J., speaks at an event to announce legislation to lower health care costs and protect people with pre-existing medical conditions, at the Capitol in Washington. In the campaign for House control, some districts are seeing a fight between Democrats saying they'll protect voters from Republicans willing to take their health coverage away, while GOP candidates are raising specters of rioters imperiling neighborhoods if Democrats win. (AP PhotoJ. Scott Applewhite, File)

FILE - In this March 26, 2019 file photo, Speaker of the House Nancy Pelosi, D-Calif., joined at left by Energy and Commerce Committee Chair Frank Pallone, D-N.J., speaks at an event to announce legislation to lower health care costs and protect people with pre-existing medical conditions, at the Capitol in Washington. In the campaign for House control, some districts are seeing a fight between Democrats saying they'll protect voters from Republicans willing to take their health coverage away, while GOP candidates are raising specters of rioters imperiling neighborhoods if Democrats win. (AP PhotoJ. Scott Applewhite, File)

Each party says their messaging is poll-tested and will work.

Public safety and police defunding are “an increasingly significant and powerful issue” in suburbs, said Dan Conston, president of the Congressional Leadership Fund. Conston, whose group is aligned with House GOP leaders, said with health care, Democrats are betting “their tired, dated arguments will work.”

“Health care is the number one issue that people care about,” counters Rep. Cheri Bustos, D-Ill., who heads the Democratic Congressional Campaign Committee, House Democrats' campaign arm. She says Democrats are “on the right side” on law and order, supporting peaceful marchers but denouncing “people who are burning buildings.”

FILE - In this March 28, 2019, file photo, President Donald Trump speaks at a campaign rally in Grand Rapids, Mich. In the campaign for House control, some districts are seeing a fight between Democrats saying they'll protect voters from Republicans willing to take their health coverage away, while GOP candidates are raising specters of rioters imperiling neighborhoods if Democrats win. (AP PhotoManuel Balce Ceneta, File)

FILE - In this March 28, 2019, file photo, President Donald Trump speaks at a campaign rally in Grand Rapids, Mich. In the campaign for House control, some districts are seeing a fight between Democrats saying they'll protect voters from Republicans willing to take their health coverage away, while GOP candidates are raising specters of rioters imperiling neighborhoods if Democrats win. (AP PhotoManuel Balce Ceneta, File)

So far, public polling offers scant evidence that the GOP's law and order arguments have taken hold.

A Monmouth University Poll this month showed voters nationally trust Democratic presidential nominee Joe Biden slightly more than Trump to maintain law and order. It also found just 13 percent say it's highly likely that integrating suburbs would worsen crime and harm property values.

A September survey by The New York Times and Siena College found that while majorities in swing states Wisconsin and Minnesota called lawlessness a major U.S. problem, few considered it a primary concern at home.

A Biden for President sign in a lawn of suburban Dublin, Ohio, on Friday, Sept. 18, 2020. In the campaign for House control, some districts are seeing a fight between Democrats saying they'll protect voters from Republicans willing to take their health coverage away, while GOP candidates are raising specters of rioters imperiling neighborhoods if Democrats win. (AP PhotoJulie Carr Smyth)

A Biden for President sign in a lawn of suburban Dublin, Ohio, on Friday, Sept. 18, 2020. In the campaign for House control, some districts are seeing a fight between Democrats saying they'll protect voters from Republicans willing to take their health coverage away, while GOP candidates are raising specters of rioters imperiling neighborhoods if Democrats win. (AP PhotoJulie Carr Smyth)

Republicans say they've detected growing support on the issue since last month's violence in Kenosha, Wisconsin, after police shot a Black man. This summer's racial justice protests have been largely peaceful, but images of violent ones have received widespread attention.

Defunding police “is an absolute loser with suburban voters,” said GOP consultant Liesl Hickey. She said the issue is a twofer because it “plays into the bigger fear of what they see as the radical left."

Still, Republicans say they must use the theme carefully.

Signs in support of President Donald Trump and other Republican candidates on a lawn of a suburban Dublin, Ohio, home on Friday, Sept. 18, 2020. (AP PhotoJulie Carr Smyth)

Signs in support of President Donald Trump and other Republican candidates on a lawn of a suburban Dublin, Ohio, home on Friday, Sept. 18, 2020. (AP PhotoJulie Carr Smyth)

“I think Democrats are vulnerable to it," said Sam Geduldig, who advised former House Speaker John Boehner, R-Ohio. “But the harder you go on it, the more it turns off some of those wealthy suburban voters in some districts we need."

In 31 House races where Democrats have aired ads and Bustos’ organization is helping them, spots in 28 contests make health care arguments, according to committee figures.

One attacks Republican Nick Freitas, challenging Democratic Rep. Abigail Spanberger outside Richmond, Virginia. It criticizes him for accepting insurance company contributions and favoring repeal of Obama's health care law, even when the pandemic means “Virginians couldn't be more in need” of coverage. Freitas has said he thinks government intrusion into health care doesn't help.

FILE - In this June 5, 2018, file photo Orange County Supervisor Michelle Steel smiles as she visits Rep. Dana Rohrabacher's election night party in Costa Mesa, Calif. Republican challenger Michelle Steel has talked about taxes, while Democratic Rep. Harley Rouda has focused on health care and prescription drug costs. In the campaign for House control, some districts are seeing a fight between Democrats saying they'll protect voters from Republicans willing to take their health coverage away, while GOP candidates are raising specters of rioters imperiling neighborhoods if Democrats win. (Jeff GritchenThe Orange County Register via AP, File)

FILE - In this June 5, 2018, file photo Orange County Supervisor Michelle Steel smiles as she visits Rep. Dana Rohrabacher's election night party in Costa Mesa, Calif. Republican challenger Michelle Steel has talked about taxes, while Democratic Rep. Harley Rouda has focused on health care and prescription drug costs. In the campaign for House control, some districts are seeing a fight between Democrats saying they'll protect voters from Republicans willing to take their health coverage away, while GOP candidates are raising specters of rioters imperiling neighborhoods if Democrats win. (Jeff GritchenThe Orange County Register via AP, File)

Democrats have run health care themed ads against Republicans in numerous states including Colorado, Illinois, Indiana, Nebraska and Texas. According to data from the ad-tracking company Kantar/CMAG, Biden’s campaign has run a spot in around 30 states. In it, he promises to protect people's coverage “the same way I would my own.”

So far, Republicans have used law and order themes more selectively, including in New York and Nebraska. In Michigan, GOP Rep. Fred Upton has run a spot criticizing Democratic opponent Jon Hoadley, a state lawmaker who opposed a resolution urging local governments to not defund police departments.

“The political extremists have gone too far,” the ad says as protesters smash storefronts. On his campaign website, Hoadley says he favors changes such as training officers to avoid racial bias.

In a coastal district south of Los Angeles, Republican challenger Michelle Steel has talked about taxes, while Democratic Rep. Harley Rouda has focused on health care and prescription drug costs.

Recent Trump ads have largely emphasized restoring the economy, not blazing buildings. Many House GOP ads also use other issues, accusing Democrats of backing tax increases and linking them to House Speaker Nancy Pelosi, D-Calif., a favorite foil.

Even so, according to Kantar/CMAG, one Trump campaign spot that's run this month in a half-dozen states accuses Biden of wanting to defund the police.

“The radical left has taken over Joe Biden,” the announcer says as protesters batter windows. It adds, “Don't let them take over America.”

Biden has repeatedly said he opposes defunding the police.

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Salter reported from O’Fallon, Missouri. Associated Press writers Amy Taxin in Los Angeles and Marc Levy in Harrisburg, Pennsylvania, contributed to this report.