President Trump with House Speaker Paul D. Ryan (R-Wis.) in the Rose Garden after the House passed its health-care bill this month. (Evan Vucci/Associated Press)

There is a kind of unspoken arrangement between President Trump and congressional Republicans. It goes a little something like this:

TRUMP TO REPUBLICANS: I will help you pass your agenda now that the GOP controls Washington!

REPUBLICANS TO TRUMP: We will do our very best to put up with your tweets, shenanigans and general tomfoolery in service of that goal.

It has been an uneasy accord since Day One. But never has it been under more duress than it is now.

Analysts, including me, have been fond of suggesting that Trump won't truly be in trouble as long as the GOP base remains intact, and that base hasn't even come close to deserting him. In fact, Trump voters are much more likely to say he has exceeded their expectations than say he has disappointed them — by a lot.

And from that standpoint, it's not difficult to see why speaking out against your party's president and alienating those many passionately pro-Trump conservatives isn't all that appealing to Republicans in Congress. From a strictly self-preservation standpoint, you don't need to be inviting any unnecessary primary challenges.

But there's another very pragmatic calculus in all of this that I think congressional Republicans are confronting right now — irrespective of the base question. It's not whether they think supporting Trump is good for their political futures, but whether it actually helps them pass their agenda.

Given the trajectory of developments over the past eight days — from firing FBI Director James B. Comey, to admitting that the Russia investigation played a role in it, to sharing highly classified information with Russia, to having asked Comey to shut down the investigation of former national security adviser Michael T. Flynn — Republicans must be wondering whether any hope is left for legislation. These sideshows and self-inflicted wounds and unforced errors (almost every single one of which is for Trump) have eclipsed any real efforts to pursue a health-care bill, tax reform or an infrastructure program.

Now one-12th of the way through Trump's four-year term, no legislative payoff is in sight. What is in sight are more investigations and a whole bunch of difficult questions from the media about why the president thinks it's okay to:

  1. Fire the guy who is investigating you
  2. Ask the FBI to stop investigating your former top aide
  3. Discuss highly classified information about the Islamic State with an adversarial foreign power
  4. Give completely contradictory information to the American public, over and over again

None of these controversies have easy defenses, apart from shouting “FAKE NEWS” or “BUT WHAT ABOUT THE LEAKERS?” Even if you don't think Trump firing Comey or urging him to shut down the Flynn inquiry constitutes obstruction of justice, it certainly isn't a good thing. The same goes for giving classified information to Russia. There's just no satisfactory answer.

Much of the conservative media has given up trying to cover for Trump, instead simply ignoring or giving short shrift to these stories of major consequence; it truly has been remarkable to watch. And TV news is apparently having a very difficult time booking any Republican guests to stand up for this administration. Witness this:

That's telling. Defending Trump is the job that never ends, and the ratio of time spent defending Trump to time spent passing conservative legislation is woefully lopsided.

The counter-argument to all of this, of course, is that Trump got them a Supreme Court justice! And that's no small thing. Having a credible Republican president in place would certainly be helpful if another vacancy comes along.

But at some point, Republicans have to wonder just how much credibility Trump has left and how much his loose lips and penchant for manufacturing his own controversies is conducive to all of them doing their day jobs. If there's little hope of any real progress on legislation — and the ship seems to be preparing to leave port on that count — what point is there in fighting for this president anymore?

Far be it from me to predict the End of Trump. Journalists have been predicting that since he launched his campaign; that's not the point here.

The point is that the end could come even before Republican voters start heading for the hills. In the end, a fractured agenda might be just as damaging to Trump as a fractured base.

Update: To the point above, New York Times political guru Maggie Haberman reports that Senate Republicans are reconsidering their Comey game plan. Why? Because they're worried it will torpedo what's left of their agenda.