For all the Sturm und Drang of the bill's passage last night, there's a simple reason House Democrats ultimately provided the votes to pass the CRomnibus, and always were going to provide the votes to pass the CRomnibus: they didn't have a better alternative. If the CRomnibus collapsed, what came next would have been worse for Democrats.

(Confused about what the CRomnibus is, or why it has that name? Head here.)

The CRomnibus funds the government — with the exception of the Department of Homeland Security — through fiscal year 2015. But Republicans had a Plan B. If the CRomnibus hadn't passed, they would pass a three-month stopgap spending bill. Then the next Congress could worry about how to fund the government through the rest of the year. It was actually a pretty reasonable Plan B — which is why it scared Democrats. If there was going to be a shutdown over this, it was going to be up to Democrats to cause it, and it was going to be Democrats who took the blame for it.

The key dynamic of the CRomnibus fight is in the two words "next Congress". The next Congress is a lot more Republican than this one. Whatever deal Democrats could get in this Congress, with Harry Reid in charge of the Senate, was going to be better than the deal they could get in the next Congress, with Mitch McConnell in charge of the Senate and more Republicans in the House.

But precisely because Democrats knew that, and Republicans knew they knew that, Democrats couldn't get a very good deal in this Congress, either. Republicans could walk away from the table more easily than Democrats.

You could hear this echo through the comments of Dick Durbin, a liberal senator who's also a member of the Appropriations Committee. "I think the progressives within the Senate Democratic caucus are feeling they have to speak up," he told the Washington Post. "Most of those who are vocal and active have never been in the minority. I listen to them and I think, ‘They’re not aware that this place is going to change a lot in just a few weeks.’ "

For the Democrats negotiating the bill, the coming of the Republican Congress was an omnipresent threat. It's why the White House ended up lobbying House Democrats to pass a bill nobody liked.

But House Democrats did the White House a favor on Thursday. A year from now, the Republican Congress is going to have to figure out how to fund the government in 2016. And Obama is going to be the only Democratic veto point. With the near-collapse of the CRomnibus, Elizabeth Warren and House Democrats gave him a lot more ammunition to tell Republicans there there are deals he simply can't sell to his liberal wing, and so will have to veto.

It's a play Republicans and the Tea Party have been running against the White House for years now. There's a deal on the table that seems like a compromise, but Speaker Boehner says it's still not conservative enough to sell it to his members. The play only works because House conservatives are credible in their defection threats. House liberals just got a bit more credible in theirs.