There will be a significant phone call made in Washington today. It may even be happening as I write this. President Joe Biden and Senator Joe Manchin are going to talk directly to each other in an effort to strike some sort of deal on Biden's Build Back Better agenda -- call it a summit of the Joes.

Manchin, of course, is never at a loss for reasons why he still can't bring himself to publicly support the bill being crafted in the Senate. These reasons shift over time and he's always willing to create new ones if previous issues he has raised have already been addressed. Months ago, he called for a "pause" on the whole process, which must translate to: "let's just not do anything for another year or two," since no matter how much time passes he still seems to feel no sense of urgency whatsoever.

Biden is going to need to communicate to Manchin the desperate sense of urgency the entire rest of the Democratic Party now feels. Manchin has gummed up the works for almost the entire year now (Biden proposed the Build Back Better bill a few months after he took office, after all), while other Democrats have just gotten more and more frustrated with his stubborn obstructionism. Manchin, to his credit, has never completely torpedoed the bill -- he just keeps creating new reasons to oppose it, while remaining coy about whether he'd vote for it or not if forced to. This keeps all the attention on him, which has to be at least part of the reason why he's doing it. Manchin has been on television more in the past year than he has during his entire political career, which he seems to enjoy immensely. Who wouldn't? Rather than being some nameless "one out of 100" senator from West Virginia, he has instead become the pivotal power broker in Washington, to the point where people jokingly refer to him now as "President Manchin."

But enough is enough. The real tragedy of Manchin's continued slow-walking of the Build Back Better bill is that it has eclipsed pretty much everything else important in Joe Biden's agenda. There are any number of issues which need legislative action, but none of them will get the attention they deserve until Build Back Better is done. Joe Manchin, aided and abetted by Kyrsten Sinema, has wasted almost an entire legislative year. If the Democrats lose either house of Congress in the midterms, this will represent half the time Biden will have had to get anything done.

The next two weeks are going to be crucial. Up until now, several self-imposed deadlines have been created in an attempt to pressure Manchin to make up his mind, but none of them has done the slightest bit of good. Manchin just scoffs at them, blowing through deadline after deadline without doing anything but continuing to waffle. But this time there is a real deadline -- one with actual consequences. If the Build Back Better bill doesn't pass by the end of this year, tens of millions of American families are not going to get their monthly Child Tax Credit checks in mid-January. Or any month after that -- the program will just suddenly stop. This time, inaction has a pretty steep political price.

The checks themselves are one of the biggest achievements of Democratic control of Congress this year:

It's not just that the credit has proven a revolutionary policy change that has dramatically slashed child poverty. It's also that it has managed to unify Democrats, amid a year of factional infighting, in a way few other policies have. What's more, this policy presents a chance to be a defining legacy item for the Democratic Party of the future.

. . .

Interestingly, this whole affair doesn't map neatly on to conventional battle lines in our politics. Not only does this Democratic policy help boost red state America; here is a case where Manchin's opposition threatens and angers moderate and centrist Democrats as much as progressives.

"It really comes down to Manchin against the world," Samuel Hammond, director of poverty and welfare policy at the Niskanen Center, told me.

On top of all this, Hammond notes, the child tax credit has the potential to become a defining pillar for the Democratic Party, in a manner perhaps similar to Social Security in the last century.

"Letting this program lapse is squandering a chance for the Democratic Party to cement a lasting legacy," Hammond said.

That's the sort of thing that hopefully Joe Biden will be making clear to Joe Manchin on the phone today. This isn't some sort of game, real people's lives are about to be very negatively affected if Manchin continues to stall. This includes plenty of parents in West Virginia, a fact which Manchin doesn't seem to care much about.

But then, it's hard to know exactly what Joe Manchin does care about, at this point. Other than being the center of attention.

The clock is now ticking in a tangible way. This is not some sort of consequence-free deadline created out of thin air by Chuck Schumer or Nancy Pelosi. The I.R.S. has informed Congress that if it doesn't renew the program for the coming year by December 28th, then January's mid-month checks will not go out. If this comes to pass, Joe Manchin is going to own all the bad press that results as the program expires. Comparisons will no doubt be made to Ebenezer Scrooge, and it's going to be hard to argue with that portrayal.

Again, one hopes that Joe Biden makes this crystal clear on the phone today. If Build Back Better does not pass by the end of the year, Democrats won't have much to run on in next year's midterms. This was already going to be a tough election, and the only chance Democrats really have is to convince the voters that they're better than the alternative: "You put us in charge, and we are getting things done." Without Build Back Better, they simply won't be able to realistically make this case.

Joe Manchin has already done enough damage to Joe Biden's agenda. He has forced Biden to scale back his ambitions by roughly half. That's bad enough. But half a loaf would still usher in a whole lot of fundamental changes for the better for the American people. Chuck Schumer is still aiming to hold a vote on the bill before Christmas. If Manchin votes "No" on it in the end, he will not only have wasted almost an entire year of Biden's term, he will have personally torpedoed the Democratic Party's chances of retaining power in Congress next November. That will be Joe Manchin's legacy.

Once again, I certainly hope Joe Biden explains this during the "Joe summit" today. Joe Manchin can either be remembered as the senator that saved the Democratic Party's agenda or the one who drove a stake through its heart. Those are the choices he faces. And the clock has almost run out of time.

-- Chris Weigant

Follow Chris on Twitter: @ChrisWeigant