Former Republican Speaker of the House Newt Gingrich predicted Monday that Hillary Clinton will not be the Democratic presidential nominee and the "science fiction"-like Donald Trump will likely just "keep winning."

Fox News' Greta van Susteren invited Gingrich to comment on the current state of the presidential race, starting with Republican frontrunner Donald Trump.

Describing Trump as someone "totally different from anybody in modern politics," Gingrich said that if another candidate doesn't effectively "take him head on," he's just going to "keep winning."

"The other candidates have to face the reality that if he stays at 25 or better, he wins," said Gingrich. "If you have 15 or 17 candidates and one of them has 25 percent, they keep winning. So someone is going to have to, sooner or later, is going to have to take him head on. And so far the people who have tried to take him head on don't do very well."

Van Susteren agreed, saying Trump responded to attacks by rolling over opponents "like a Mack truck."

"He's like a science fiction film, where you shoot at him and he gets bigger," added Gingrich.

Van Susteren then turned the conversation to the beleaguered Hillary Clinton. "Is Sec. of State Hillary Clinton going to be the nominee?" she asked.

"I don't think so," replied Gingrich. "I think they're probably going to find a minimum of 1500 emails that are involved with ... national security issues."

Though he predicted she would likely "implode," Gingrich added that Republicans "should worry" about Vermont Sen. Bernie Sanders.

"If Hillary starts to implode you will see a vacuum that you have not seen in many, many years," said Gingrich.

If that should happen, Gingrich said he could see Michael Bloomberg, Jerry Brown, Elizabeth Warren, or even Sec. of State John Kerry jumping in.

Gingrich also said he doesn't believe that Clinton can count on President Obama to protect her, nothing that there's "no love lost" between them after their bitter primary duel.

Video via RCP.