Mitt Romney on Friday became the highest-profile Republican to vow not to vote for Donald TrumpDonald TrumpFundamentals or euphoria? Both fueled post-election stock surge Freedom Caucus founder: GOP health plan did not meet campaign promises Former US envoy: No good military options against North Korea MORE if the controversial businessman becomes the GOP presidential nominee.
“I’ll either vote for a conservative who runs or I’ll write in the name of a conservative," Romney said during an interview on the "Fox Business Network" on Friday.
"I’m going to vote for the nominee, but it’s not going to be Donald Trump," Rubio said on a radio program.
“I can’t even imagine that, and I don’t even want to imagine that right now, to be honest with you. I don’t believe it’s ever going to happen. It’s one of those bridges you hope you never have to cross," he added.