Sen. Rand Paul (R-Ky.), whose 2016 presidential ambitions now look like a sure thing, slammed potential rival Mitt Romney on Wednesday, saying a third attempt at the Oval Office by the former Massachusetts governor would be “the definition of insanity.”

“When you do the same thing and expect a different result, it’s sort of what Einstein said, that the definition of insanity is to do the same thing over and over again and expect a different result.” Paul told the New Hampshire Journal of another possible Romney candidacy.

The Kentucky Republican added that he admires Romney, but that the two-time failed candidate should follow his own advice.

“A couple of months ago he said that he’d had his chance and it was time for somebody new,” Paul said. “He was probably right when he said that.

“I think we do need somebody and something new,” Paul continued. “We had a great 2014 but really a presidential election is a completely different election. Twice as many people vote and a lot of the people who vote in presidential elections seem to vote for the Democratic Party.”

Paul also questioned fellow possible 2016 contender Jeb Bush’s ability to bring new life to the GOP, saying that the former Florida governor is too similar to Romney.

“[Romney and Bush] occupy the same space and are competing somewhat for the same voters — people who want something that is safe, something that is sort of historical,” Paul said. “But even people who are looking for ‘safe’ realize that ‘safe’ hasn’t won in the past.”

Though he says he won’t formally announce his candidacy until spring, Paul said that his campaign would take a fresh approach aimed at bringing new voters to the GOP cause.