According to Public Policy Polling:
Our new poll finds that Trump is benefiting from a GOP electorate that thinks Barack Obama is a Muslim and was born in another country, and that immigrant children should be deported. 66% of Trump's supporters believe that Obama is a Muslim to just 12% that grant he's a Christian. 61% think Obama was not born in the United States to only 21% who accept that he was. And 63% want to amend the Constitution to eliminate birthright citizenship, to only 20% who want to keep things the way they are.
Trump's beliefs represent the consensus among the GOP electorate. 51% overall want to eliminate birthright citizenship. 54% think President Obama is a Muslim. And only 29% grant that President Obama was born in the United States. That's less than the 40% who think Canadian born Ted Cruz was born in the United States.
Trump's supporters aren't alone in those attitudes though. Only among supporters of John Kasich (58/13), Jeb Bush (56/18), Chris Christie (59/33), and Marco Rubio (42/30) are there more people who think President Obama was born in the United States than that he wasn't. And when you look at whose supporters are more inclined to think that the President is a Christian than a Muslim the list shrinks to just Christie (55/29), Kasich (41/22), and Bush (29/22).There's more, but it's not for the faint of heart.