Whatever else Donald Trump does for the rest of the 2016 GOP campaign, one thing is clear: He should not allow others to call the shots.

Drawing a comparison to a former president, Ronald Reagan biographer Craig Shirley said Reagan, for instance, bowed to pressure from the national media and hired experts to help produce “white papers” on a variety of topics in 1979 and 1980.

“Reagan did it pretty badly,” said Shirley. “They spent a lot of money on white papers by professors. They did it because the press kept hounding him.”

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Shirley, who has compared the Trump phenomenon to Reagan, said the problem with getting too specific is that a candidate opens himself up to critics who then parse every detail.

“You’re chasing your tail, and you’re never going to catch it,” he said. “My advice would be to do what feels comfortable.”

There is more than one way to demonstrate seriousness. Trump could, for instance, deliver a serious policy speech. “I think that would probably be a good idea, but keep it general. Keep it in broad strokes,” Shirley said.

To date Donald Trump has defied expectations and rocketed to the top of the Republican presidential primary field with direct talk and bold promises, largely unsupported by policy details. Many political observers believe he can continue to ride that wave for awhile — but that he’ll eventually need to flesh out his rhetoric in order to expand his support.

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“At some point he’ll have to get more detailed, but for now he can get by on personality,” said Candice Nelson, academic director of the Campaign Management Institute at American University in Washington. “If he’s serious about really running, he’s going to have to do that.”

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So far, the “positions” section of his campaign website includes just one entry — a much-ballyhooed paper on immigration. Even that, Nelson said, is briefer than the typical campaign policy paper.

Trump routinely says China is ripping off the United States on trade, but he has not explained exactly how he’d get a better deal. He has ripped President Barack Obama’s nuclear deal with Iran but has not proposed an alternative or explained how he’d achieve a promise that four U.S. prisoners jailed in Iran would be back home before his inauguration, if elected.

And the billionaire real estate developer gets applause when he says he would call the CEO of Ford Motor Co. and pressure him not to build a plant in Mexico; but Trump does not lay out what policy levers he’d pull.

It hasn’t mattered so far. Trump has led almost every national poll in the GOP race for two months. His RealClearPolitics average stands at 29.8 percent — 12 points ahead of second-place Ben Carson.

Some attacks hurled at Trump in recent weeks have focused directly on the lack of clarity in his positions.

“From his point of view, he would probably follow the old adage: If it’s working, don’t change it,” said Chris Arterton, a professor of political management at George Washington University. He predicted earlier than most analysts, he added, that Trump would have staying power. “As long as there is a big field of candidates, he probably will (keep doing) just what he’s been doing.”

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Some attacks hurled at Trump in recent weeks have focused directly on the lack of clarity in his positions. Former Florida Gov. Jeb Bush reminded a crowd in New Hampshire that Trump has changed his positions on health care and other issues.

“We’re a conservative party, aren’t we?” Bush said. “Mr. Trump doesn’t have a proven conservative record. He was a Democrat longer in the last decade than he was a Republican.”

“Will he have to get more specific? The answer is yes. But I think that comes about more likely in March or April.”

The risk for Trump is that, eventually, some of this criticism will start to stick, particularly as more voters learn of statements he has made and positions he has taken over the years that are out of step with the party.

“I think we maybe are seeing the peak for Donald, just given the negatives,” said Arterton, founding dean of George Washington’s Graduate School of Political Management.

One way Trump could break through that ceiling, Arterton said, is by laying out more specifics. But Trump probably will not do that until the field begins to narrow after the Iowa caucus, he said.

“Will he have to get more specific? The answer is yes. But I think that comes about more likely in March or April,” said Arterton. “We will see some of those. I’m not sure when.”

The real test, he added, is what happens if Trump starts to fade.

“How he reacts to that, whether he doubles down on the bombast or transforms himself in a more serous candidate, I think is a guess,” he said.