Donald Trump’s assertion that he would make Muslims in America register in a database has forced candidates of both parties to stake out clearer positions in the heated debate over security after the Paris attacks.

It’s a more fraught conundrum for the Republicans, many of whom are jockeying for positions along the hardline against Syrian refugees entering the U.S. But the three Democratic candidates hit back strongly against Trump’s claim.

Former Secretary of State Hillary Clinton called the comments “shocking” and implied that meant Trump is unfit to be president:

Former Maryland Gov. Martin O’Malley used even harsher language, telling MSNBC Friday: “When you hear people like Donald Trump talking about wanting to do ID cards based on religion. What the hell is that? I mean, how is that at all American?”

Vermont Sen. Bernie Sanders weighed in Friday afternoon, saying Trump’s comments were “bigoted” and echoing the tone of his fellow Democratic candidates:

Read More: Republicans Push Back on Trump

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Write to Tessa Berenson at tessa.berenson@time.com.