Since January, America's major news outlets have dedicated themselves wholeheartedly to documenting the persistent loyalty of President Trump's most fervent supporters. "In hardscrabble Midwestern town, faith in Trump is unflagging," reads the headline of approximately 18,000 articles published over the last four months. And it goes beyond those die-hards: While Trump's overall approval is mired in the low 40s, his approval among Republicans has stayed between 85 and 90 percent, about what recent presidents have come to expect from their own partisans.

But with Trump's firing of FBI Director James Comey kicking the Russia scandal into high gear, is there any reason to believe that Republican voters — all of them, not just those who love him most intensely — won't stick behind President Trump?

We have no idea yet what the full dimensions of the scandal are; indeed, it seems like each hour brings a new juicy detail about Comey's firing. But one thing that seems sure is that it won't go away anytime soon. To understand how different groups of voters might view it, we have to think about what kind of information they're getting.

Let's stipulate that we might discover incontrovertible evidence of actions so shocking that no one of any political stripe could possibly defend them. Perhaps there's a recording of Donald Trump and Vladimir Putin discussing how Putin will deploy his cyberwarriors against Hillary Clinton, to which Trump pledges in exchange not to interfere with his expansionist plans in Europe, then they laugh as they drown a bag of puppies in the Moskva. But short of that, you'll always find some in the president's party who will defend him, and not just those in his employ.

And what the president's allies do is absolutely critical. No Republican is going to be persuaded of Trump's malfeasance by an argument she hears from Chuck Schumer or Rachel Maddow or Paul Krugman, no matter how well-articulated it might be. If she hears Democrats saying one thing and Republicans saying another, her tribal impulses will lead her to discount the former and believe the latter (and for the record, this is no less true of Democrats). We don't evaluate arguments separately from our feelings about the people making them; the two go together.

This is one of the lessons of past scandals: No matter how damaging the information, the president is safe as long as everyone important on his side — his allies in Congress, friendly media figures, and so on — stays behind him.

This factor seems again and again to determine how a scandal will end. The Lewinsky scandal never stopped being clearly drawn along partisan lines, so Democrats never abandoned Bill Clinton. Even just before Richard Nixon's resignation, when the depths of his criminality had become plain to see, his approval among Republicans bottomed out at ... around 50 percent, according to Gallup. It was only when a significant number of Republicans in Congress turned against him that he resigned (and that only happened with the release of damning audiotapes).

Likewise, in the depths of the Iran-Contra scandal — in which, for those of you too young to remember, the Reagan administration sold arms to an Islamic theocracy and used the profits to fund an illegal war in Central America — Ronald Reagan's approval among Republicans never dropped below 73 percent. When things got really bad for George W. Bush near the end of his term, with a cascade of failures culminating in the Great Recession, his approval among Republicans fell to around 60 percent.

All of which is to say that presidents can almost always count on most of their partisans staying loyal, no matter how bad things get. President Trump's problem is that while he has the support of most Republicans, almost no one else is behind him. So he can't afford to start losing anyone in his own party, or his approval rating will slide down the toilet.

This all takes place within a circular process involving elected officials and the public. If their constituents turn against Trump, it will be in the interests of Republican members of Congress to do so as well, and their opposition would in turn signal to Republican voters that party loyalty does not demand sticking with the president, thereby feeding the cycle. On the other hand, if the politicians stay loyal, that sends a signal to Republican voters that only Democrats are opposed to the president, reinforcing the partisan cast to the issue and keeping them in the fold, which in turn means that the politicians have no incentive to defect.

The calculation will be slightly different for each member of Congress, and you can predict what they'll do by looking at their district. For instance, Rep. Barbara Comstock (Va.) is one of the few Republicans who have been openly critical of the Comey firing; she is also almost alone among her GOP colleagues in calling for an independent investigation into the Russia scandal. Is that because she's personally some kind of bipartisan moderate? Hardly — she made her bones in politics as a knife-in-her-teeth opposition researcher, digging up dirt on the Clintons in the 1990s. But she represents a swing district in the affluent Virginia suburbs just outside Washington, D.C.; Hillary Clinton beat Trump in her district by 10 points. Which makes her acutely aware that defending Trump will threaten her re-election bid next year.

But right now, she's in a tiny minority. Meanwhile, the places where many conservatives get their information, like Fox News and conservative talk radio, are manning the barricades in Trump's defense. So everything your average Republican voter is hearing convinces them that the president is right and this is all nothing but a fake scandal drummed up by Democrats jealous of how great Trump is making America.

There may come a point where the cracks in Republican unity begin to grow wider. But it will only happen when elite Republicans see it in their own interest to jump ship.