Presidential candidate Sen. Bernie SandersBernie Sanders2020 Democrats make play for veterans' votes 2020 Dems put focus on stemming veteran suicides The Memo: Democrats confront prospect of long primary MORE (I-Vt.) says Donald TrumpDonald John TrumpGOP senators balk at lengthy impeachment trial Warren goes local in race to build 2020 movement 2020 Democrats make play for veterans' votes MORE is appealing to Americans' "bad instincts" on illegal immigration.

"I have really, very strong concerns with Trump and other Republican candidates appealing to really some bad instincts in the American people," Sanders said on MSNBC's "Andrea Mitchell Reports."

"You do not call people from other countries, in this case Mexicans, rapists or criminals. You don't categorize a people like that," he continued.

ADVERTISEMENT

Trump, the GOP front-runner, has made cracking down on illegal immigration a centerpiece of his bid.

Sanders is also viewed as a political outsider and is surging in the polls, but he has rejected comparisons to Trump. He reiterated on Tuesday that he considers Trump's remarks on immigrants "racist."

Trump and other GOP candidates are headed to their party's second debate on Wednesday night. It comes two days after the real estate tycoon addressed thousands during a rally in Dallas.

"Clearly Trump is touching a nerve," said Sanders, who has attracted his own crowds in the tens of thousands. He also suggested Trump's support was a rebuke of establishment GOP candidates.