Former Speaker Gingrich to Donald Trump: Don't Go There on Bill Clinton and Women

— -- Newt Gingrich has some advice for Donald Trump: don’t bring up Bill Clinton’s past marital infidelities in the next presidential debate.

“You’re never going to beat the Clintons in the mud. It’s not possible. They’re the best gutter-fighters we’ve seen in our lifetime,” Gingrich said in an interview with ABC News Chief White House Correspondent Jonathan Karl and Political Director Rick Klein on the ABC News’ Powerhouse Politics Podcast.

"I mean you have to go back to Richard Nixon to find anyone with the potential to fight with her. So you’ve got to stay above her. You’ve got to say look, ‘ I’m going to beat you on jobs, I’m going to beat you on trade, I’m going to beat you on taxes.’”

"I thought what he did last time in not bringing it up was to his advantage," he said.

Gingrich, the former Speaker of the House and an informal adviser to the Trump campaign, is himself a veteran of the debate stage. He said that while he thought Trump won the debate, he should do more preparing.

“At a tactical level, he’s not nearly as good as a debater," he said. "It wouldn’t take much for him to be 20 or 30 or 40 percent better than he is now.”

Still, he says, let Trump be Trump. “He’s an amateur, and he’s a businessman. He’s never going to match up with a Yale lawyer who’s spent her entire lifetime trying to be glib.”

Gingrich pointed at Clinton’s mention of Alicia Machado, the former pageant queen who says Trump called her “Miss Piggy” after she gained weight during her Miss Universe reign.

“You know, she’s got to win on the grounds that he doesn’t have the temperament to be president. And she’s got to win by scoring points off 20-year-old conversations with a woman who has a very dubious past, by the way,” said Gingrich. “I mean Machado is being glorified by the left as the perfect victim. And this is why you’ll see a temporary drop in Trump’s polls because for four days he’s been piled on by the media. Just go look at the coverage but I don’t think in fact that strategically she won that debate. And I think if anything she’s in trouble in the long run because she can’t answer any of the big questions."

In an interview on "Good Morning America," Machado said that as a mother, she's "very worried he could be president." "Maybe he will be saying bad things about me or try and discredit to me. But it's OK. I'm strong."

Gingrich is out next month with a political thriller, Treason, about a female president facing homegrown terrorism. When asked what he would call a novel about this stranger-than-fiction election, Gingrich had another one word title--an apparent nod to the unlikely Republican nominee--“Wildcard.”