Senator Elizabeth Warren’s proposed wealth tax is putting her at odds with some of Wall Street’s wealthiest, and the fight is increasingly spilling out into the open.

In an interview on business new channel CNBC Thursday, billionaire investor Leon Cooperman said Warren’s plan to impose a new tax on the nation’s richest people would “penalize success” and that a Warren presidency would mean “big trouble” for Wall Street and the country.

The Massachusetts senator has made an issue of income inequality in her campaign for the White House. One of her key proposals is a 2% tax on every dollar of an individual’s wealth above $50 million.

But as Warren has gained in the polls, the reaction from Wall Street and the financial industry has become louder and more antagonistic.