If many Cruz supporters are to be believed this may be accurate. I do not actually believe this is true. In the last presidential election most of the conservatives now supporting Cruz, who were very upset about Romney being the nominee eventually fessed up... that actually held their noses and voted for him.
It was the evangelical voters who sat out that election. Many couldn't stand the thought of voting for a Mormon. This has been confirmed by numerous studies of why George in 2004 received over 4,000,000 more than Mitt Romney did in 2012.
This does not appear to be a factor with Trump. He actually received more evangelical votes than Cruz did in South Carolina. This is despite Cruz getting the support of more evangelical leaders and working very hard for their votes.
Most, but not all of the people here who prefer Cruz will still support Trump in the general. Cruz supporters know that if the Democrats win... the repercussions this time will be so incredibly awful that Cruz supporters will not sit out the election even if he is not the nominee.
Speaking of Romney, I voted for him with no enthusiasm, but not because he was Mormon, but because he is a wuss. I think he would have made a decent president, though. In that second debate with Obama, when he chose not to bring up Benghazi, told me all I needed to know about Romney.
Romney thought he was going to win and I read in the last year, Romney was so certain he was going to win, he did not have a concession speech ready. They had to scramble to put one together.
He was ahead in the polls, but decided to play prevent defense. He let Obama define him and did not respond well. I put the blame on Romney.