A Muslim-tracking database could come to the U.S., if Donald Trump is elected president.

The Republican front-runner told NBC News on Thursday that he "would certainly implement" a database to track Muslims in the U.S. He added that Muslims would "have to be" legally obligated to sign into the system.

"It would stop people from coming in illegally," he said. "We have to stop people from coming into our country illegally."

Politicians on both sides of the aisle took issue with Trump's idea. Jeb Bush called Trump's comments "just wrong," and Hillary Clinton called the remarks "shocking rhetoric."

The database idea also drew comparisons to Nazi Germany.

"What else can you compare this to except to prewar Nazi Germany?" Council on American-Islamic Relations spokesperson Ibrahim Hooper told NBC News.