Mitt Romney Says a Donald Trump Presidency Would Lead to 'Trickle-down Racism' "Seeing this is breaking my heart," he says of presidential campaign.

PARK CITY, Utah  -- Mitt Romney said today he respected prominent Republicans who have decided to back Donald Trump, but he got visibly emotional explaining why he couldn't bring himself to do the same.

"These things are personal. I love this country. I love the founders, I love what this country is built upon and its values, and seeing this is breaking my heart, for the party that means so much," said Romney, choking up and blinking back tears.

Speaking to a crowd of roughly 300 political and business leaders at his annual summit in Park City, Romney said he worried about the example a Trump presidency might set for future generations, that it would lead to "trickle-down racism."

Still, Romney insisted he understood those that have decided to back the presumptive Republican nominee, and said that he wouldn't be spending the next six months trying to convince anyone not to vote for Trump.

"I really understand both points of view about the pro- and contra-Trump setting, and respect people on both sides of this," he said.

"You listen to Paul Ryan, who I have enormous respect for, I don’t argue with him at all (...) and I wouldn't suggest for a minute that he ought to change his position and adopt the one that I've taken," he went on.

The choice of whether to back Trump, Romney said, comes down to whether Republicans care more about the Supreme Court (the next president could appoint as many as four Supreme Court justice) or the example a Trump presidency might set for future generations.

Romney said Trump would be more likely to appoint justices who would defend conservative values, but that he was more concerned with the latter, arguing, "Bill Clinton’s dalliances in the White House affected the sexual practices and inclinations of a generation and probably beyond."

"Both [Clinton and Trump] are destructive. I think that's the frustration many people in this room and many people around the country feel," he went on.

Asked why he had reached out to Trump for his endorsement when he was running for president in 2012, Romney replied that at that time Trump hadn't said the things he said this cycle. Trump’s focus on "birtherism" -- questioning President Obama's birthplace -- back then was "nutty" but not xenophobic, racist, or misogynist.

Romney also condemned the other GOP candidates this cycle for failing to take Trump on sooner.

He criticized Texas Sen. Ted Cruz for praising Trump until he realized that wasn’t working, Jeb Bush and his super PAC for spending so much money attacking people other than the frontrunner, and Ohio Gov. John Kasich for staying in the race too long.

"I think their biggest failure was not focusing on the frontrunner, and instead focusing on each other," he said.

Still, he conceded that Trump "won fair and square" and had a "very effective strategy" that capitalized on people's anger and frustration.