One of Donald Trump’s few redeeming qualities is that he always betrays and humiliates anyone foolish enough to ally with him. Over the weekend, Trump directed his ire at Energy Secretary Rick Perry and Senator Mitt Romney, who once cravenly auditioned to be Trump’s secretary of state. On Saturday, Trump claimed it was Perry who urged him to phone Ukrainian President Volodymyr Zelensky—and was thus to blame for the Ukrainegate scandal. On the same day, Trump went on a Twitter tirade against Romney, one of the very few elected Republicans to offer any criticism of Trump’s abuse of presidential power to collect dirt on his political opponents. Trump also urged that Romney be impeached (a remedy that isn’t available against senators in the Constitution). As icing on the cake, Trump called Romney “a pompous ‘ass.’”

Trump’s attacks on Perry and Romney were a way of disciplining those around him in the White House and inside the GOP tent; a reminder that he’s more than willing to implicate, tarnish, or sideswipe anyone who crosses him.

This internecine quarreling among Republicans is taking place as Ukrainegate continues to mushroom. On Sunday, the Associated Press reported that during the very period Rudy Giuliani, the president’s lawyer, was pressuring the Ukrainian government to investigate Joe Biden and his son Hunter, friends of Giuliani and Trump were touting their ties to the president while seeking to gain access to Ukrainian gas companies.

Amid the ballooning scandal, there has been continuing chatter about possible GOP defections. Reporting in The Washington Post, Robert Costa and Philip Rucker wrote: “A torrent of impeachment developments has triggered a reckoning in the Republican Party, paralyzing many of its officeholders as they weigh their political futures, legacies and, ultimately, their allegiance to a president who has held them captive.” They suggested that three other Republican senators (Ben Sasse, Lamar Alexander, and Richard Barr) could join Romney in the rank of Trump critics.

CNN political analyst Sarah Isgur offered a similar assessment, reporting “a lot of quiet conversations among conservative thought leaders today about how to prepare for a ‘post Trump’ Republican Party—whether its [sic] impeachment or a loss in 2020.”

The salient word here is “quiet.” You would need a seismograph of extreme sensitivity to register any sign of a Republican rebellion against Trump. Aside from Romney, who has had harsh words but still doesn’t say he will vote to remove Trump, there have simply been no GOP dissents of note. The Never Trump faction of the GOP has been a shrinking sect since 2016. Many erstwhile Trump opponents within the GOP abjectly surrendered after he won the presidency and scored important right-wing victories on tax cuts and court appointments. Emblematic of the shift is pundit Erick Erickson, who in 2016 described Trump as a “racist” and fascist” that would “never” win his vote.” This past week Erickson titled a blog post “I Support the President.”

Trump rules the GOP through a combination of fear and hope. The fear was well described by a former senior Trump official who told The Washington Post, “Nobody wants to be the zebra that strays from the pack and gets gobbled up by the lion.” This analogy is a little off, zoologically. The zebra is a creature of genuine nobility, while most Republican elected officials belong to more docile and domesticated species—like sheep or cows.

It’s their bovine or ruminant nature that makes Republicans so easily herded by the carnivore Trump. They fear the fate of Mitt Romney, a Twitter lashing from their master. Hence they come up with ridiculous excuses for Trump, like the now-common line that his comments asking China to investigate the Bidens was just a joke. “I doubt the China comment is serious,” Senator Roy Blunt said. His colleague Marco Rubio has uttered a similar mealy-mouthed evasion.

But it’s not just fear of Trump’s wrath that motivates Republicans. They also have hopes for their party and their own individual prospects. Unlike the Watergate scandal, this impeachment impinges on an election. Trump is almost certain to be the party’s standard-bearer in 2020. Tarnishing him with impeachment, let alone removing him with a Senate vote, would carry huge political costs.

There is one way in which Watergate is relevant, though: The lesson of the previous scandal was that there is no political incentive to be an early advocate of impeaching a president of your own party. As historian Rick Perlstein showed in his 2014 book The Invisible Bridge: The Fall of Nixon and the Rise of Reagan, Watergate was a boon to Ronald Reagan because it allowed him to earn a reputation among partisan Republicans as a loyal party man. Reagan in 1973 and 1974 was among the most fervent defenders of Nixon, even though the beleaguered president carried out policies that Reagan disagreed with, like détente with the Soviet Union. Reagan described Watergate as “a lynching” and Nixon as a “a truthful man.” Reagan even defended Nixon’s crooked Vice President Spiro Agnew. “I have known Ted Agnew to be an honest and honorable man,” he said in 1973. (Agnew would resign in disgrace the following year.)

During Watergate, pundits like David Broder of The Washington Post were puzzled by Reagan’s behavior. Why was he fastening himself to the sinking ship of Nixonism? In fact, Reagan’s steadfast partisanship made him a hero to the Republican rank and file. Beyond Reagan, the politicians who stuck with Nixon to nearly the end (George H.W. Bush and Bob Dole) had a better future in the party than the ones who jumped ship early (like Howard Baker).

The incentive structures in the Republican Party are clear. Criticizing Trump will make you a pariah. Sticking with Trump gives you a future in the party, perhaps even a presidential nomination one day. Mitt Romney is likely to be a lonely man for the foreseeable future.