At least since Donald Trump first announced his presidential campaign in June 2015, journalists and activists have been asking: Is this the scandal that finally does him in?

Would his casual description of Mexican immigrants as rapists in his announcement speech force him to drop out shortly after he jumped in? Would his attack on John McCain for being captured in Vietnam end his campaign? What about mocking a disabled New York Times reporter? Or lying and saying Muslim Americans in Jersey City celebrated the 9/11 attacks? Or proposing an all-out ban on Muslim immigration?

What about the revelation of a tape where he brags about sexually assaulting women? Or the stories from multiple women who confirmed he did, in fact, sexually assault them? Or firing the FBI director to impede an investigation into his administration? Or leaking highly classified information to the Russian government? Would any of these be enough to finally bring Trump down?

As it turns out, the answer in each case was no. None of these were enough to stop Trump from winning the presidency, or to force him out of it. And there’s no indication that the revelation that Trump ordered FBI director James Comey to close his investigation into former National Security Adviser Michael Flynn will be any different.

So far, congressional Republicans are keeping their heads down and waiting for more information. Senate Intelligence Committee chair Richard Burr told reporters, "I think the burden is on the New York Times [which broke the story], if they're reporting it and they've got somebody who's got the document. They need to get the document and get it released."

It's a remarkable statement. Rather than stand up to his president, calling emergency hearings, or otherwise use his powers to address the wrongdoing, a Republican senator with subpoena power is saying he won’t do anything until the press does his job for him. But Burr did better than Rep. Darrell Issa (R-CA), who literally flipped off a reporter asking about the news. Sen. Lindsey Graham (R-SC) told my colleague Dylan Scott, “If the FBI director feels the president did something inappropriate, he should come in and tell us," and dismissed the need for a special prosecutor, saying, "Nobody’s showed me a crime anywhere."

The sad truth is that whether or not Trump is “brought down” has at best an indirect relationship to the gravity of the charges against him. His fate depends much more heavily on how Republican leaders in Congress respond to the scandals in question than it does on those scandals’ details or severity. Trump is the American president. He can only be removed from office if a majority of the House votes to impeach and a two-thirds majority of the Senate votes to convict.

Unless Trump voluntarily chooses to resign, the only thing that will bring him down is Ryan and Senate Majority Leader Mitch McConnell agreeing that he must be removed from office, and rallying their members to vote for impeachment and removal.

Nixon had a Democratic Congress forcing him out. Trump doesn’t.

Yes, impeachment could theoretically proceed with mostly Democratic votes and some defecting Republicans. But in practice, both the Nixon and Clinton impeachment processes began with the full House voting to refer the matter to the House Judiciary Committee, and the Judiciary Committee approving articles of impeachment and sending them to the floor.

You can’t hold those votes unless the majority party schedules them. “Impeachment happens in the House of Representatives, and since the House is run on majority rules, it’s really up the majority party to run the process as it sees fit,” my colleague Andrew Prokop explains.

And, of course, Republicans are the majority party in the House and Senate. In the three previous impeachment scenarios in US history, the president has been faced with a congressional majority of the opposing party. Andrew Johnson, a Democratic/National Union Party president, faced a huge Republican majority in both houses. Richard Nixon faced a Democratic majority in both houses. Bill Clinton faced a Republican majority in both houses.

Trump, however, has co-partisans in charge of both houses. But surely, you may reply, Trump’s crimes trump those of Johnson, Nixon, or Clinton! Maybe (I doubt it in the case of Johnson), but it doesn’t matter what you or I think. It matters what Ryan and McConnell think. And what they really want is a Republican president to sign their priorities, in particular slashing health care and other social programs and cutting taxes, into law.

Impeachment would wreck Republicans’ legislative agenda

Impeachment proceedings are long and ugly and almost completely consume Congress’s time and energy. They take up months that Republicans desperately need to pass health care and tax legislation before the 2018 midterms, which could see them lose control of the House. Think about it from Ryan’s perspective. He has, by his own admission, wanted to cut health programs for poor people since he was drinking out of kegs in college. So he can either charge forward with that goal and push for final passage of the American Health Care Act — or he can spend months and months impeaching the president and giving a massive political gift to Democrats instead.

If you take the cause of cutting social programs and taxes as seriously as Ryan does, then why the hell would you ever choose the route of impeachment? He’d be left with very little time to enjoy the relative predictability and lower scandal output of President Mike Pence before the midterms put his House majority in danger. And if the 1974 midterms are any indication, having your party’s president leave under dint of scandal is a great way to lose an enormous number of seats in the House and Senate. After that, Ryan’s dream is dead.

The much easier path for Ryan and McConnell is to continually minimize Trump’s wrongdoing and decline to investigate seriously, let alone look into removal.

Maybe it doesn’t require impeachment, though. Maybe Trump will voluntarily resign if the situation gets bad enough. I mean, maybe. But is there anything about Trump’s character and temperament that makes such an outcome seem plausible? Nixon refused to resign until his party’s leaders in Congress came to him and told him impeachment was inevitable. Would even that do it for Trump? Why would he give Ryan and McConnell the gift of an easy departure were they to betray him like that?

As political scientist Julia Azari notes, impeachment is not about the law. Not really. It’s not a prosecution where a dispassionate prosecutor weighs the evidence, takes it to a grand jury, gets indictments, and then has a normal trial. It’s a political proceeding. A president survives if fewer than 218 House members and 67 senators want him out; otherwise, he falls.

For Trump to fall, for a scandal to end his presidency, what’s needed isn’t a new, massive scandal. What’s needed is for Ryan and McConnell to decide that investigating and prosecuting Trump is important, and the right thing to do. I hope they make that a priority. I hope they force Trump to appoint an independent prosecutor with the ability to recommend impeachment charges, and push through the impeachment charges if the prosecutor deems them warranted.

But the matter is in Ryan and McConnell’s hands, and no one else’s. As long as they remain on Trump’s side, the president is going nowhere.