A former candidate to lead Britain's Conservative Party has thrown her support behind front-runner Boris Johnson.

Andrea Leadsom, an ardent backer of Britain's exit from the European Union, told LBC Radio that she's backing Johnson, because "I think he will be a very good leader for our country."

Leadsom's endorsement came as the leadership contenders move to a knockout round and television debate Tuesday.

British Conservative party leadership contender Boris Johnson gets in a car as he leaves his home in south London, Tuesday, June 18, 2019. Contenders for leadership in Britain's ruling Conservative Party to become the next Prime Minister, jostled for attention Monday as the race narrowed into a contest to seize the mantle of challenger to front-runner Boris Johnson. (AP PhotoMatt Dunham)

British Conservative party leadership contender Boris Johnson gets in a car as he leaves his home in south London, Tuesday, June 18, 2019. Contenders for leadership in Britain's ruling Conservative Party to become the next Prime Minister, jostled for attention Monday as the race narrowed into a contest to seize the mantle of challenger to front-runner Boris Johnson. (AP PhotoMatt Dunham)

The goal is to win the coveted slot on the postal ballot being sent to Conservative Party members nationwide — a vote that will decide the next leader and the next prime minister.

The contest will choose a replacement for Prime Minister Theresa May, who stepped down as party leader earlier this month after failing to secure Parliament's approval for her Brexit deal.

Follow AP's full coverage of Brexit and the Conservative Party leadership race at: https://www.apnews.com/Brexit