Sarah Kendzior is a St. Louis, Mo.-based commentator who writes about politics, the economy and media

In October of 2016, Utah Republican Jason Chaffetz, the head of the House oversight committee, announced that he was pulling his support for Donald Trump.

"My wife and I, we have a 15-year-old daughter, and if I can't look her in the eye and tell her these things, I can't endorse this person," he said, after Mr. Trump's boasts of sexual assault came to light.

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Like all things related to GOP integrity, Mr. Chaffetz's commitment was short-lived. It's now been seven months since Jason Chaffetz has been able to look his daughter in the eye, busy as he has been defending the groper-in-chief and dodging questions about his complicity in the Russian interference scandal. Until recently, Mr. Chaffetz refused to investigate Michael Flynn and other Trump associates.

Now Mr. Chaffetz, tainted by Trumpian treachery, is stepping down, telling CNN: "At some point, you've got to get off this crazy train. There's always somebody doing something stupid somewhere, there's always plenty of things to investigate and look at."

He is right. The crazy train is the Trump Train, and it runs down its own passengers. A politician may think he is riding the train, only to find out the train's been riding over him, pounding him into political roadkill. Survivors of the Trump Train stumble around like scared animals who don't understand how they mistook the highway for home. Just ask Chris Christie, the first major Republican to endorse Mr. Trump, and now the first to condemn him, as he pitifully affirmed this week the corruption of the administration he was not asked to join.

Logically, there was never any incentive to board the Trump Train. The President has spent his whole life acting like Faust only without an actual soul to sell, striking bad bargains that humiliate whoever joins him. Trump's promises never hold: Support this lifelong con artist and you will sacrifice yourself for nothing. Ask Sean Spicer, whose dream of seeing the Pope this week Trump denied. In Trump's America, the train rides you.

One would think, with a 40-year track record of malfeasance and an administration under investigation by multiple intelligence agencies, that the GOP would realize it is finally time to leave the Trump Train. The stakes are as high as they can get: The fate not only of the U.S. but of the world rests on their ability to put country over party, to rein in Mr. Trump's violent ambitions and to investigate Mr. Trump as the public demands.

Unfortunately, the GOP shows few signs of wising up. There are three main reasons for this: careerism, opportunism and contamination. The first, careerism, is the most simple to understand and overcome. GOP candidates are concerned about re-election and refuse to denounce others in the party. As Mr. Trump's popularity plunges, the risk of careerism lessens.

Then you are left with opportunism. Many who boarded the Trump Train likely did so suspecting the conductor might get booted, leaving them with Mike Pence, a right-wing extremist who nonetheless is a more standard Republican official. Opportunists are fighting to get vile policies – like stripping Americans of their social safety net – passed before Mr. Trump is potentially booted while simultaneously avoiding the contamination of his regime.

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But this endeavour is impossible. As GOP strategist and "Never Trumper" Rick Wilson says, "Everything Trump touches dies." This includes the ability of politicians to escape unscathed. If it is only one's career prospects and integrity that are lost, the politician is lucky. At this point, association with the Trump administration means you may be tangentially linked to a massive international criminal operation. It means you may be in proximity to treason, as some have perceived from the released tapes of Speaker Paul Ryan and others speculating that Mr. Trump might be paid by Russian President Vladimir Putin.

The road to impeachment is the road to self-immolation, which is why Republicans at Russian interference hearings behave as if intelligence officials – like former CIA chief John Brennan – are hostile witnesses instead of patriots providing valuable testimony, and treat leaks as greater affronts than the horrifying revelations the leaks contain.

National security should never be a partisan issue. The gutlessness of the Republican Party at this critical juncture hurts all Americans, including themselves. To depart the Trump Train now may be to leave tarnished by scandal, but it is the only way to keep the country from going off the rails.