Donald Trump is not going to quit the race. The Republican party is not going to push him off the ballot. He may have a brief surge in the polls at some point, because the first rule of politics is that all races tighten.

Then again, maybe not. It could be that Trump's surge came and went during the final week of July and that the tightening period has already passed. But while we're talking about things that are not going to happen, understand this: Donald Trump is not going to win.

Trump isn't just behind in the big battleground states. No, what should scare sense into any sophisticated Republicans is that Trump is clinging to bare leads in Utah, Kansas, and South Carolina. He's behind in Georgia. This is not a presidential race. It's The Poseidon Adventure.

If Trump were any other figure, Republican party elites would be making cold-blooded calculations about pulling the plug.

But because Trump commands a sub-rational cult of personality, Republicans seem committed to sticking with him, no matter the embarrassment, no matter the cost. And the real perversity is that they seem to be doing it not because they like Trump but because they hate him.

It's almost as if Republicans who caved to Trump now feel compelled to stick with him now as a way to justify their earlier mistake: We're going to prove to you how not-craven we were, even if it means wrecking the party.

An intervention is needed. So like Rick Santorum discussing abortion with Barbara Boxer, let us go back to first principles.

Can it ever be wise to pull the plug on a presidential campaign? Of course it can. When a campaign has no reasonable path to victory and the candidate at the top of the ticket is a drag on the down ballot elections, decisions must be made. There are two ineluctable truths of campaigns: Resources are finite and candidates matter.

If, on October 15, Trump is down 15 points and vulnerable senators such as Kelly Ayotte, Rob Portman, Pat Toomey, and Richard Burr are within the margin of error in their races, it would be a no-brainer for Republicans to shift all available resources away from the presidential contest and to the state elections. (This is what happened with Bob Dole in 1996.)

So if such a strategic calculation would be valid in late October, the question isn't whether or not it can be made, but only when it should be made. Perhaps mid-August is a little early. Then again, perhaps not. Because the utility of those marginal dollars decreases every week you wait to execute the shift. If you favor withholding resources from vulnerable senators for a few more weeks so as to give Trump the chance to reset the race, that's fine.

But understand that decision comes with a cost, and at this point we are merely haggling over price. The general principle has been established. The RNC and big money donors (who are holding a Hamptons fundraiser this Saturday) are going to pull the plug eventually. The longer they wait, the less help they'll be to congressional Republicans.

That's the money side of the equation. There is also the question of endorsements. Never before has there been a moment when disavowing a presidential nominee could be electorally helpful. Then again, we have never seen a nominee like Donald Trump. To give you just one example: A Reuters/Ipsos poll this week noted that 44 percent of registered voters want Trump to drop out while only 35 percent say they intend to vote for him.

Read that again. We have arrived at a place where Trump's support is dwarfed by the proportion of people who just want him to go away. This is truly undiscovered country.

So the question is, if, come October, Trump is still deeply unpopular—and that GOP Senate candidates are outperforming him by wide margins—will it make sense for Republicans to disavow Trump? Especially since there will be a good chance Trump could say or do something to tip the race against them in the final days? After all, why should the Senate seats become hostage to a malicious presidential candidate?

Again, the answer is almost surely yes. And so, once again, we are at the stage of prudential calculation: Not if Republicans should abandon Trump publicly, but when will be the optimal time to do so.

Because as with money, there is opportunity cost involved. If a Senate candidate's best chance of victory is to portray themselves as an independent check on whomever is president, they need time to establish their bona fides.

As a smart political friend notes, down-ballot Republican candidates should:

Try to take advantage of the growing assumption that Hillary will win and the deep distrust of her—particularly among Republicans and translate them into a call for Republicans of all preferences to turn out to keep our congressional majorities. Not to do good (which was the mistake of 2010 and 2014), but to prevent bad. Boiled down, the message should be: "If Hillary Clinton wins in November and voters also put Democrats in control of Congress, then Bernie Sanders and other extreme liberals will be calling the shots in Washington. If you want to stop the Democrats from imposing their liberal agenda then no matter whom you support for President you must get to the polls and vote Republican for Senate and Congress this November."

If Republican congressional candidates cut Trump loose now, they'll get credit for it with voters, who will at least give their pitch a hearing. Every week they wait, the eventual disavowal becomes less potent.

But there is one more bit of opportunity cost at play.

If Trump loses, then beginning on November 9 the GOP will begin scrubbing his taint from the party. If you think this will be short work, consider that Democrats were able to hang George W. Bush around Republicans' necks for eight years. The longer Republican office holders continue their embrace of Trump, the more likely it is that Democrats will be able to brand the GOP as a crazy, racist Trumpian institution in 2018, or 2020, or beyond.

Many of those who hold out hope for some gigantic exogenous event or character pivot to intervene in the race have pure motives. They're worried about the Supreme Court and the future of conservative principles. That's fine.

What these people do not understand is that the White House is already lost this cycle and the Supreme Court with it. Every day spent defending the indefensible Donald Trump is a day not used trying to preserve senators and House members who will be able to fight Hillary Clinton's agenda. The longer Republicans deny this reality, the more catastrophic the results will be. At this point, the only real question about the Trump campaign is whether it will end in catastrophe for Republicans, or extinction.

Because the first rule of finance is the same as the last rule of politics: Never throw good money after bad.