Donald Trump's path to the Republican nomination looks clear, Mitt Romney said Sunday, but that won't stop the former Massachusetts governor from trying to throw some obstacles in the billionaire's path.

Romney returned to his anti-Trump talking points in an interview on CNN's "State of the Union" with Gloria Borger, reiterating much of the message from his address last Thursday. The 2012 Republican presidential nominee once again called for voters to support whichever candidate has the best chance of defeating Trump in a given state, be it Gov. John Kasich in Ohio or Sen. Marco Rubio in Florida.

Even that, Romney admitted, may not be enough to stop Trump.

"I do know that when my grandkids say, 'What did you do to stop Donald Trump?' I wanted to be able to say something," Romney said, adding later that "At this stage, we say all right, he could easily become the nominee, probably most likely to be the Republican nominee at this point, but I think there's a better choice out there."

Asked by Borger if he regretted not jumping into the presidential race given the direction has taken, Romney offered an emphatic no and recalled telephone conversations with his wife Ann Romney in which she called the 2016 campaign "so degrading, so demeaning." Romney also refused to entertain the notion of jumping into the race at a contested Republican National Convention this summer.