Republican Nebraska Sen. Ben Sasse came out strongly against Donald Trump Monday, saying the presumptive GOP nominee’s attacks on the judge handling the lawsuits against Trump University classifies as “racism.”

Public Service Announcement:

Saying someone can’t do a specific job because of his or her race is the literal definition of “racism.” — Ben Sasse (@BenSasse) June 6, 2016

Trump has said that the judge presiding over the lawsuits against Trump University has an “absolute conflict” of interest because of his “Mexican heritage.”

Sasse has been one of the loudest Republican lawmakers to attack Trump. Sasse has called the New York real estate developer a “tiny little man.”