The trouble keeps stacking up for President Donald Trump: No major legislative success on Capitol Hill, pointed criticism from fellow GOP lawmakers and previous Republican presidents blasting his approach to government, a special counsel probe that recently ensnared three campaign advisers and a Democratic sweep of the Nov. 7 gubernatorial races in New Jersey and Virginia.

For any other president, this would seem like key ingredients for a primary challenge in the next election. But, as America has learned in the year since he was elected, Trump isn’t like any other president.

In interviews with nearly three-dozen GOP strategists and fundraisers over the past several tumultuous weeks, virtually everyone told me that – barring some major personal embarrassment in the Russia investigation – they expect Trump to coast to the GOP nomination in 2020.

Yes, there’s plenty of handwringing within the GOP about Trump’s presidency. Earlier this fall, Arizona Sen. Jeff Flake and Nebraska Sen. Ben Sasse were frequently discussed as potential challengers for Trump. Flake went so far as to say Trump’s actions were “inviting a challenge.” But lately, the most vocal Trump critics within the GOP, such as Flake and Tennessee Sen. Bob Corker, are exiting the political stage entirely – and in the process, potentially clearing the way for more Trump loyalists to move to Washington.

“The primary process is going to be dominated, just as it was in 2016, by the most vocal, the most ardent Trump supporters.”

“The primary process is going to be dominated, just as it was in 2016, by the most vocal, the most ardent Trump supporters,” said Republican strategist Kevin Madden, who advised Mitt Romney’s 2012 presidential campaign and is a CNN political commentator. If Trump were to draw an opponent, those voters “would be focused on guarding against a primary challenger who could be destructive in the general election.”

Trump’s political future is, of course, deeply uncertain and could well depend on the results of special counsel Robert Mueller’s investigation and whether Democrats can retake the House in next year’s midterm elections. And modern political history has plenty of examples of incumbent presidents such as Gerald Ford, Jimmy Carter and George H.W. Bush staring down primary fights.

But the hurdles to a 2020 primary challenge are vivid when considering a recent Washington Post/ABC News poll that found 91% of Trump voters said they’d vote for him again. That means the idea of another Republican dislodging Trump in the 2020 primary remains, for now, a liberal fantasy —one that vastly underestimates the institutional power of the presidency, the desires of GOP donors, and the fact that the Republican National Committee is essentially built to support the incumbent running for re-election.

“The email lists, the voter files, as well as donor lists — from major donors to low dollar donors — all of that is sitting there (at the RNC) to help the President get re-elected when that time comes,” said Henry Barbour, a GOP strategist and longtime RNC member. “There would be plenty of discussion about voter lists and what the RNC controls, but it would be challenging for any (Trump opponent) to get their hands on the best lists that the RNC controls — and that matters.”

Spencer Zwick, Romney’s former fundraising chairman, said from the money standpoint alone, the hurdles of successfully executing a primary challenge against a sitting president would be daunting.

“Incumbency has a huge advantage as it relates to the money,” Zwick said. “All of the money that is being raised today for the party, that’s all ultimately going to flow up to the incumbent,” he said, pointing to the investments the party is making in its field operation and voter data collection. “They can take advantage of that now, and also in the general election.”

Several bundlers who raised money for other GOP candidates in the 2016 cycle also said there is little appetite among donors right now for supporting a Trump challenger. As one donor put it: “It doesn’t even rise to the level of discussion.” A Republican strategist who opposed Trump in 2016, noted that most donors view a Trump primary challenge as “kamikaze mission”— one that would “just allow a Democrat to win.”

The four primary challenges that have occurred since 1968, when Eugene McCarthy took on Lyndon B. Johnson, are a testament to that thinking. Weakened by the Vietnam War, Johnson announced he would not run for re-election. Ford was weak when Ronald Reagan challenged him in 1976; Carter’s vulnerability drew Ted Kennedy into the 1980 race. Pat Buchanan’s challenge of Bush in 1992 sowed division within the GOP, weakening him in his three-way race with Ross Perot and Bill Clinton in the general election.

“Most primary challenges to an incumbent president have not been successful, but they have been determinative in shaping the outcome of the general election where the incumbent who was challenged lost.”

“Most primary challenges to an incumbent president have not been successful, but they have been determinative in shaping the outcome of the general election where the incumbent who was challenged lost,” said Steve Schmidt, a top strategist for 2008 Republican nominee John McCain and someone who has criticized the President.

Trump has faced a remarkable backlash within his own party during the first year of his presidency. Corker, who is retiring, has questioned the President’s stability and competence and referred to the White House as an “adult daycare center.”

In an extraordinary speech from the Senate floor as he announced that he would not seek re-election, Flake warned that if the politics of Trump and his former chief strategist Steve Bannon were to triumph, Americans would become a “fearful, backward looking people.” But Flake, who has been frequently mentioned as a potential Trump opponent in 2020, acknowledged that he was stepping down, in part, because he was unlikely to win the primary in his own state and was unwilling to do what it would take to win.

Others who have taken on Trump, like McCain and the former Bush presidents are at the stage of their careers that are far beyond presidential politics.

At this moment, Schmidt said, most of the top players in the Republican Party seem paralyzed in their embrace of Trump, shrinking away from the battles he invites with his mocking tweets and criticism of his own party.

To take on Trump in 2020, “You’d need toughness, principle and the communication ability to reunite the conservative movement around the idea of the Republican Party being the party of ideals and solutions—a party that’s not run by crazy people,” Schmidt said.

“You need someone who’s not intimidated by the Breitbart convention, somebody who has the capacity to understand that the power of Steve Bannon and Ann Coulter is illusory,” Schmidt said. He described a culture of timidity and fear, where some Republican leaders are acting like “prey animals” who are “constantly skittish, looking nervously over their shoulders for the predator who is about to get them.”

Any Trump opponent would also need to match the President’s talent for drawing free media and defining the daily narrative. Terry Sullivan, who ran Marco Rubio’s 2016 presidential campaign, described the ability to get earned media attention as the top criteria for any Trump foe.

“It’s one of these situations where money almost doesn’t matter, because you need more than money,” Sullivan said. “An ability to get media attention is going to be critical.”

“We’re in a brave new world of politics these days, so anything is possible,” he went on.

Someone like Mark Cuban, the entrepreneur and Dallas Mavericks owner, “who would force Trump into responding—could be a deadly candidate against him,” Sullivan said.

Cuban recently said that if he were to run, he would run as a Republican. In an email, he underscored that he was not “committing to anything,” and believes “the only smart strategy right now is to not focus on where things are today.”

“To me the biggest underlying issue is that it needs to be someone who can stand up to Trump.”

“To me the biggest underlying issue is that it needs to be someone who can stand up to Trump,” Cuban said in an email when asked about whether he would entertain a 2020 challenge to Trump. Someone who can “throw punches back harder than him, and spend 100% of their time with his base talking with them one on one, city by city, and letting them see what real respect for their situation is, and what real solutions sounds like.”

If Trump does draw a primary challenger, the Reagan-Ford matchup of 1976 serves as a useful historical lesson about the power of incumbency to sway party leaders and delegates.

Reagan’s challenge to Ford was so serious that the two men fought it out all the way through the Republican convention, with advisers to both men contemplating a “co-presidency” until that idea was quashed by both sides.

Ford campaign adviser Stu Spencer and Reagan campaign adviser Charlie Black still laugh about their daily battles over delegates during that 1976 campaign cycle. Spencer noted that in Reagan they were facing a far more talented candidate, who was the ideological heir apparent within the party, while Ford was an accidental candidate dealing with all of Richard Nixon’s Watergate baggage.

“He had the heart of the party… There were delegates who voted for us in Kansas City (at the convention) who had tears in their eyes, because we used the institution to break through to the party base at the delegate level,” Spencer said. “That could mean a hundred different things. You had Air Force One that you could give them a ride on. You’ve got the Oval Office you could invite them to. If it was a farm vote that you needed, you could get the Secretary of the Agriculture to deliver it.”

Black recalled traveling the country during 1976, and visiting an uncommitted delegate at his home in Pennsylvania. “I’d get him leaning toward Reagan, and that person would have dinner at the White House the next night.”

“You can use the White House for all kinds of perks,” Black said.

In 1976, Ford’s aides became experts on the wishes and desires of each delegate that they needed to sway. They arranged interviews for the young relatives of delegates who were seeking jobs in Washington, and engaged in discussions with delegates about who they wanted nominated to serve as judges on the federal bench.

In one case, Spencer told Ford that to win the vote of delegate, he needed to pardon two of the delegate’s friends. (Ford said no.)

“The West Wing of the White House when I was doing the Ford campaign thought I was awful – I was making commitments galore,” Spencer said. “Trump has no qualms about doing things like that – it’s part of his deal-making.”

“No matter how unpopular he becomes,” Spencer said, “he still has all of those tools.”