The political maneuvering about infrastructure is getting pretty strange, what with President Biden first cheering a bipartisan bill, then threatening to veto it, and then taking back the veto threat in the span of two days. When the action on stage gets hard to follow, it can be helpful to review the main characters and their motivations.

The 21 bipartisan dealmakers in the Senate want to see their bill passed not just because they think it would improve the country’s roads and bridges but because it would reduce the likelihood that Congress will take two other steps: passing a Democratic bill that spends additional trillions on child care and raises taxes, and weakening the filibuster.

Senate Majority Leader Chuck Schumer had planned to spend June building the case against the filibuster, as The New York Times reported. He would advance one piece of appealing-sounding legislation after another – especially a bill that would supposedly “protect voting rights” – and then blame their demise on the excessive use of the tactic.

The infrastructure deal foiled this plan. The Senate ended its June work with a demonstration that a significant number of Republicans are willing to legislate, not just obstruct, and that the chamber can work without having to change its rules.

Progressives and most Senate Democrats, meanwhile, worry that the moderate Democrats in the bipartisan group will point to any success on the infrastructure bill as a reason to pare down or walk away from the second spending bill, which independent Sen. Bernie Sanders, the Budget Committee chairman, is preparing.

One theory for Biden’s behavior, based on both news reports and some discussions with Senate aides, is that the White House was taken by surprise when the bipartisan group reached a deal, felt obliged to endorse it, and then got scorched by progressives. To appease them, he blurted out that he would not sign the bipartisan bill without signing the second one “in tandem.” But that infuriated the moderate Democrats, so he had to backtrack.

House Speaker Nancy Pelosi is still keeping the pressure on the moderates, though, saying she will not allow the House to vote on the bipartisan bill until the Senate has passed the partisan one. It’s a strategy that will require stubbornness.

It will take weeks to convert the bipartisan agreement into legislative language. Drawing up Sanders’s bill and getting it through procedural hurdles will take months. Democrats do not yet agree even on the price tag: He has floated $6 trillion, while Sen. Joe Manchin has talked about $2 trillion. Even in today’s Washington, that’s a big difference.

Most congressional Republicans are watching the Democratic infighting from the sidelines. They oppose both spending bills.

They think we have been spending quite enough money over the last two years as it is – COVID legislation alone has added more than $5 trillion to the federal debt – and also want to deny Biden legislative victories. They don’t believe our infrastructure is crumbling, and they are skeptical that federal infrastructure spending will go where investments would do the most good.

They are right about that, by the way. It’s true that the American Society of Civil Engineers says that we are in dire need of more spending on infrastructure. If there’s a National Society of Barbers, it probably thinks we all need more haircuts. And Congress is not exactly laser-focused on using an infrastructure bill to maximize the country’s productivity.

Getting a win for Biden, stopping him from getting one, influencing the debate over the filibuster: These are the type of considerations that are on the top of legislators’ minds. Unsurprisingly, then, much of the negotiation has turned on arbitrary spending levels and not, say, on which projects deserve funding and which do not.

Polling suggests that the public likes the idea of infrastructure spending but doesn’t see it as a high priority. Democrats decided to make it a top issue, and now they are running the risk that by holding out for everything they will get nothing.

If the bipartisan infrastructure deal fails, it won’t be because the Senate is dysfunctional. It will be because the Democratic Party is.