Ben Carson is sticking by his claim that Islam is inconsistent with the U.S. Constitution — a claim that earned him a lot of backlash, even from fellow Republicans. (Video via C-SPAN)

"I think Dr. Carson needs to apologize," Lindsey Graham said.

It doesn't look like he will. His spokesperson told NBC that Carson "just doesn't believe the American people are ready" for a Muslim president.

His comments came after Trump failed to correct an audience member at a rally who said President Barack Obama was Muslim. (Video via CNN)

Rep. Keith Ellison, who in 2006 became the first Muslim elected to Congress, weighed in on both candidates, calling them "out of touch with who we are as a people."