The U.S. Senator for Massachusetts and anti-Wall Street firebrand took to Twitter to call Trump a “loser” and call out his business record. Warren is seen widely as one of the most progressive members of the Senate, was considered by many to be the leader of the anti-financial sector movement before Bernie Sanders’ presidential campaign took off. Before campaigning for 2016 began, some pegged Warren as a potential contender, but she declined.

Let’s be honest – @realDonaldTrump is a loser. Count all his failed businesses. See how he cheated people w/ scams like Trump U.

— Elizabeth Warren (@ewarren) March 21, 2016

Warren could still be in play for the vice-presidential nomination, though with Hillary Clinton likely to be the presidential pick it seems likely that the party will want a male candidate for VP.

Still, Warren’s attack will likely sting Trump. Other than insults about his body parts, calling into question his ability as a businessman and a self-proclaimed winner have been the two things that get the Republican frontrunner most riled up.