So far, most of the attention on the progress of President Joe Biden's economic agenda has been on the bipartisan infrastructure deal. It went first, so it got the spotlight first. Now that the Republicans and Democrats seem to be in the final stages of hammering out a deal, the attention is soon going to shift to the second part of the plan: the budget reconciliation bill that will be designed to make it through the Senate solely with Democratic support.

As I've been pointing out, the most interesting thing about this bill is that Senator Bernie Sanders is in charge of writing it. Bernie's not on the outside looking in anymore, he now chairs the Senate's budget committee. And he's about to flex his power for the first time. Although the key will be (as always, these days) what Senator Joe Manchin will agree to. And this past weekend, this bidding game began in earnest.

Bernie made his opening move a few weeks back, casually talking about the bill being as high as $6 trillion. Progressives are demanding big movement on all sorts of issues (climate change being one of the most important) and they contend that massive amounts of money need to be spent immediately so there's no time to waste. Some progressives would even like to see a $10 trillion effort. Bernie put his marker down at $6 trillion.

Manchin, being interviewed this past Sunday, said he was imagining a bill in the $1 trillion to maybe $1.5 trillion range. He did hint he might go as high as $2 trillion. This is a pretty good opening move by him, as it is already higher than I might have predicted.

Before we get to where the two might agree, though, it's helpful to put it all into context. The Biden White House didn't really want the media to concentrate on adding up the total price of his three legs, but when the American Rescue Plan (which already passed, for COVID-19 relief) is added to Biden's proposed American Jobs Plan and American Families Plan, the total was roughly $6 trillion. The American Rescue Plan passed at $1.9 trillion, the initial bid for the infrastructure deal being worked out was $2.25 trillion, and the last part was $1.8 trillion.

As noted, what has already passed is $1.9 trillion. The bipartisan infrastructure deal is $579 billion in new spending, so we'll round up and call that $0.6 trillion. Meaning Biden is, so far, $2.5 trillion towards his goal. This would leave $3.5 trillion to go.

Can Bernie get Manchin up that high? Perhaps. If you split the difference between Manchin's publicly-stated ceiling (which was just his opening bid, remember) and Bernie's goal, you would wind up at $4 trillion. So Bernie could tell Manchin that the progressives were the ones giving in more, to get down to just $3.5 trillion.

Manchin is such a contrarian, however, that he might still balk. But at some point, Bernie will have to draw a "floor" for the lowest amount the progressives will accept. And I'm predicting (based on nothing but gut feeling, mind you) that they'll wind up right at $3 trillion. Bernie will have given in $3 trillion, and Manchin will only have moved $1 trillion, so whatever helps him get elected back in West Virginia, I suppose.

I have no doubt that Manchin will also take out a few other pounds of flesh from the deal. West Virginia is coal country, of course, so some of the more ambitious parts of the green agenda might wind up on the cutting room floor -- but not all of them. Progressives exert just as much leverage over this process as Manchin does, and if pushed too far they will defect.

If I'm right (or even in the ballpark), this will be a pretty momentous achievement. If a $3 trillion bill is passed, it will mean Biden will get $5.5 trillion out of his $6 trillion initial ask. And that is a solid victory, politically. It'll be pretty hard for progressives to complain that he missed his mark, if he gets this close to it. And when viewed in context, it will be seen an enormous and historic progressive accomplishment.

Biden's whole economic agenda will -- if it all does manage to become law -- be the largest such investment since the Great Society of Lyndon Johnson. It will be a revolutionary advancement of what good government can do for its citizens. Right now it is hard for the public to really comprehend what it will all mean -- which is aided and abetted by a media much more interested in the process of passing these bills than the actual substance of them -- but by the time the bills are drafted into legislative language, perhaps the Democrats will do an adequate job of selling all the benefits to the American public. There will be no shortage of things to talk about, since Biden's economic agenda has so many pieces to it. Free community college, free preschool, help with child care, replacing every lead water pipe in the country -- there are just all kinds of good things for Democrats to talk about.

But that can wait -- because right now, the real subject is how much of it will Joe Manchin accept? Where will his lines in the sand be drawn? Bernie Sanders is going to have to negotiate a deal with Manchin and all the other moderate Democratic senators that is still large enough not to lose progressive support. So while the focus is now on the particulars of the bipartisan deal (which should be drafted into legislative language soon), the particulars of the next bill are going to be a lot more interesting. All the negotiating over the reconciliation bill will take place within the Democratic Party, so it's going to have a different flavor to it, but the deals struck to make it acceptable to all are going to wind up being the most significant in the entire process.

-- Chris Weigant

Follow Chris on Twitter: @ChrisWeigant