OP's original question
"...to think surely nobody will vote Donald Trump now?"
The latest polls are out
"Trump Increases Lead After Call To Block Muslims Entering Country
Donald Trump took a commanding lead in the polls following his call to bar Muslims from entering the country, but his fellow Republicans may wind up paying the price.
Donald Trump’s recent remarks opened a chasm between the real estate billionaire and the rest of the Republican Party, which had been cultivating the minority vote for years.
The Donald has suffered near universal condemnation from Republicans for his call to temporarily stop Muslims from entering the country, but the billionaire continues to command a sizable lead in the polls."
www.inquisitr.com/2620335/trump-increases-lead-after-call-to-block-muslims-entering-country/
I don't think anyone believes Trump would do it or has thought it through, but that seems to have little effect on voting intentions.