Sen. Mitt Romney, R-Utah, took a series of shots at President Trump in an interview that aired Sunday, saying that some of the president's rhetoric appealed to racism and claiming that under his leadership, the U.S. was abandoning allied Kurdish fighters in Syria.
Romney, who said he wrote in his wife, Ann, when he voted in 2016, told "Axios on HBO," "The places where I would be most critical of the president would be in matters that were divisive, that appeared to be appealing to racism or misogyny, and those are the kinds of things I think that have been most, most harmful long term to the foundation of America's virtuous character."
He noted he still voted with Trump 80 percent of the time.
Trump and Romney have feuded with regularity in recent years, with Trump regularly referencing Romney’s 2012 defeat against incumbent President Barack Obama.
"Somebody please wake up Mitt Romney," the president tweeted. "If Mitt worked this hard on Obama, he could have won. Sadly, he choked!"
Romney, a former Massachusetts governor, has become one of the loudest voices on the right to condemn Trump openly.
Romney said he's felt like a renegade Republican in light of Trump’s rhetoric.
He added in the interview: "People will recognize that character really is important in our leaders and that it's important for our leaders to do things that unify us, that welcome people who come here legally as immigrants, that in no way signal to anybody in America that they're less of an American because of where they came from or their sexual orientation or their race or their religion."
Romney said the future will not be kind to Trump’s legacy, including his recent actions in Syria: "We should never abandon our friends."
"Well, clearly, the world watches and people who potentially could be our allies at a critical time say perhaps the U.S. won't stay with us. Perhaps they'll cut and run if they think it's in their best interest. And, walking away from the Kurds in a corner of Syria at a critical time when the troops coming from Turkey are intent upon doing them harm is something which I think would be a very dark spot in American history."
The Trump administration last week helped broker a deal for a 120-hour cease-fire, during which time the Kurdish-led forces could pull back from the roughly 20-mile-wide safe zone on the Turkish-Syrian border.
All Turkish military operations under the recent offensive known as Operation Peace Spring are to pause during that time, and the operation itself will come to an end entirely upon the completion of the Kurdish withdrawal, under the terms of the deal.
Trump ordered the bulk of the approximately 1,000 U.S. troops in Syria to withdraw after Turkish President Recep Tayyip Erdogan made it clear in a phone call that his forces were about to invade Syria to push back Kurdish forces, many of whom Turkey considered terrorists.
Between 200 and 300 U.S. troops are expected to remain at the southern Syrian outpost of Al-Tanf.
Fox News' Ben Florance contributed to this report.