New York CNN  — 

Bill Clinton said in an interview set to air Sunday on CNN’s “State of the Union” that he is impressed by many of the Republicans considering a presidential run in 2016, offering praise for a group that has made attacking his wife a badge of honor.

“They’ve got a lot of youth, they’ve got a lot of energy, they’ve got some significant diversity and they’re no dummies,” the former president said during an interview with CNN’s Jake Tapper at the annual Clinton Global Initiative America meeting in Denver.

“And they believe what they believe,” Clinton continued, teasing them. “They still believe trickle-down economics works better than investment and their convictions are so great that they’re undeterred by evidence and that’s always amazing to me.”

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“They’re impressive,” he added later.

One of the few things Republicans have been able to agree on in the run up to 2016 is their disapproval of Hillary Clinton, the former secretary of state and frontrunner for the Democratic nomination. The Republican candidates have made attacking her a staple of their stump speeches, and some, like business executive Carly Fiorina, have looked to use the media attention around her to get attention of their own.

“They’ll all sing in the choir about how bad Hillary was,” Clinton said to a chorus of laughs from the audience watching the interview. “And it will be difficult for those who thought she was great when she was a secretary of state and went on record saying it.”

What has most surprised Clinton? How many Republicans are running.

“There’s a lot of them. It looks more like the Kentucky Derby than Belmont,” Clinton said, noting that the field of 10 declared Republicans – with more on the way – more closely resembles the 20-horse Derby than the eight-horse Belmont. “I sympathize with the question of how the primary voters are going to decide who to vote for.”

So far, 10 Republicans have declared their plans to run for president, including Sens. Ted Cruz, Rand Paul and Marco Rubio, as well as 2012 veterans like former governors Mike Huckabee of Arkansas and Rick Perry of Texas.

It is likely that five candidates – including former Florida Gov. Jeb Bush, New Jersey Gov. Chris Christie and Wisconsin Gov. Scott Walker – will enter the race in the next month.

This varies greatly from the Democratic field that has been dominated by Hillary Clinton. Three other candidates – former Maryland Gov. Martin O’Malley, Vermont Sen. Bernie Sanders and former Rhode Island Gov. Lincoln Chafee – have jumped into the race, but none have been able to match Hillary Clinton’s standing in the polls.

Bill Clinton said that despite the number of Republican candidates, he expects primary voters will “wind up voting for the person they think has the best chance to win” in spite of their ideological dreams.

“It may be harder this year than before to figure out who’s the most electable candidate,” he said, adding later that “for an outsider who doesn’t understand all the ins and outs of it, it will make it difficult to predict” who is the most electable.

“I predict that at some point during this process, whatever they’re debating and whatever the stories are, there will be a move by people who think they can influence the process to settle on the one that’s most electable,” Clinton said, citing how Mitt Romney, John McCain and George W. Bush – the last three Republican nominees – were all viewed as the most electable when they ran.

Realizing that he didn’t give a definitive answer on who he thinks will win, Clinton said that he doesn’t know many of the Republican contenders. He did not mention, however, his close relationship with the Bush family, particularly former President George H.W. Bush, whose son is expected to announce his run on Monday.

Bill Clinton grew close to the Bush family after defeating the elder Bush in 1992. He regularly jokes that he is the black sheep of the Republican family.

After giving a wide ranging answer, however, Clinton said that even if he had a prediction, he wouldn’t let it slip.

“If I did and I thought I knew who’d win, I probably still wouldn’t say,” he said to laughs.