Noted political scientist and campaign expert Larry Sabato has a one-word piece of advice for Republican presidential front-runner Donald Trump before the next debate: “Prepare.”

During an interview on “The Laura Ingraham Show,” Sabato said that Trump, who generally received mediocre marks from pundits after last week’s GOP debate, could still be spontaneous.

“It’s no sin to prepare for a debate,” said Sabato, director of the University of Virginia’s Center for Politics.

Still, Sabato said he does not believe the debate inflicted serious damage on Trump. The candidate’s standing in polls taken after the debate show some slippage, but he remains firmly entrenched at the top of the heap. He noted that Ben Carson’s numbers have declined, but predicted he would not be hurt by comments he made over the weekend indicating that he believes a Muslim should not be president.

Sabato said the early stage of a nominating contest is more like a rollercoaster than an up-and-down escalator. He noted that former Hewlett-Packard CEO Carly Fiorina has ascended, and her rise in the zero-sum game of politics has to come at the expense of other candidates.

“That’s inevitable,” he said. “Because there’s only 100 percent.”

“The establishment normally gets what it wants, because it has the heavy concentration of money and the ability to manipulate the system,” he said.

The debate did nothing for former Florida Gov. Jeb Bush, whose poll numbers did not budge. He remains mired in the single digits. Yet bookmakers still rate him a heavy favorite to win the nomination.

The reason, Sabato said, is that the odds-makers are looking to history. Other Republican establishment favorites have managed to be nominated despite a lack of enthusiasm among grassroots conservatives.

Related: Forget Pollsters, Watch the Bookies

“The establishment normally gets what it wants, because it has the heavy concentration of money and the ability to manipulate the system,” he said. “The Republican base really didn’t want (2012 nominee) Mitt Romney. But the establishment did.”

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But Sabato cautioned that just because the establishment traditionally wins these internecine fights doesn’t mean that Bush is inevitable.

“There is no physical law in the universe that commands that the establishment will always win,” he said.

Sabato said Bush faces big hurdles, not the least of which is a reluctance by people to have the 41st, 43rd and 45th presidents come from the same nuclear family.

“What signal does that send to the world? What does it suggest about the nature of American democracy?” he asked. “The signal is not good. That’s nonpartisan. People don’t like the idea of dynasty.”