"I hope that within the next 24 to 36 hours, we can get something we agree on. If not, we're going to move forward on what I think needs to be done," Senate Majority Leader Harry M. Reid (D-Nev.) told reporters Tuesday afternoon. It's now Wednesday morning. That means we're in the filibuster endgame. And, as Reid tells it, it's all up to his Republican counterpart, Minority Leader Mitch McConnell (Ky.).

If Reid and McConnell agree, filibuster reform is dead. (Alex Wong - GETTY IMAGES)

Reid has embraced a carrot-and-stick strategy on the filibuster reform. The "carrot" is the deal he's offering McConnell. Its major provisions include eliminating filibusters on the motion to proceed and speeding the process of breaking filibusters against most presidential nominations.

The Senate's reformers are crestfallen. This is not, in their view, filibuster reform. Forget breaking the Senate's 60-vote requirement. This doesn't even make senators stand up and talk, as would be the case under the proposal Sens. Jeff Merkley (D-Ore.) and Tom Udall (D-N.M.) were pushing.

But though Reid spoke admiringly of Udall and Merkley and even apologized for undercutting their previous reform efforts, he was never really on their team. "There are two camps here in terms of what the goals are," says a leadership aide. "The upshot of the kind of reform that Merkley wants is to make legislation easier to pass. What the more veteran members, including Reid, have said all along is they're mainly focused on making things work more efficiently. To put it bluntly, that’s about moving things more quickly."

The last, best hope for filibuster reformers is that McConnell won't take Reid's deal. In that case, Reid is preparing a backup plan that includes both of the items in the Reid-McConnell talks and one more: An innovative reform that changes who bears the burden for cloture votes.

Right now, the majority needs to supply the 60 votes to break a filibuster. The minority only needs one vote on the floor. Under Reid's backup plan, the burden would be reversed: The minority would have to supply the 41 votes required to keep a filibuster going, while the majority wouldn't have to do much of anything. That means that if the minority only had 38 votes present in the room, the filibuster would end. It also means the minority could be forced to muster all their people to vote at times of the majority leader's choosing: say, 3 a.m. on a Saturday. It would make filibustering a much more unpleasant experience.

In that way, it satisfies a central priority of the Merkley-Udall talking filibuster, in that it forces the minority to actually put some work into filibustering. As Sen. Amy Klobuchar (D-Minn.) told me in the New Yorker: “Some of these people who put in these filibusters simply object and go home for the weekend. We think we need to inconvenience them.”Even Merkley is supportive. “I think switching from 60 to 41 would be very valuable,” he told Slate.

But the 41-vote policy is not Reid's preference, and presumably, it's not McConnell's, either. It would also mean that Senate Republicans could go nuclear in response, shutting everything down. It would also, interestingly, mean House Republicans could go nuclear. House Speaker John A. Boehner's office released a statement saying that "Any bill that reaches a Republican-led House based on Senate Democrats’ heavy-handed power play would be dead on arrival." Reid would, all things considered, prefer to avoid that particular showdown. So his hope is that the threat of the 41-vote change leads McConnell to accept his package of more limited reforms. It's only if McConnell walks that Reid will pick that fight.

Behind this debate, say multiple Senate staffers, is the simple fact that Reid and some of the other senior Democrats really don't really want to change the filibuster. They remember being in the minority, they remember all the policies they blocked, and they prefer to keep the filibuster strong for the day they lose power. They're frustrated by what they see as Republican overuse of the filibuster and they want to make the Senate work more efficiently, but they don't particularly want to make it work very differently. It's only if they come to believe that Republicans won't, under any circumstances, allow the Senate to operate more efficiently that they'll even consider making it work differently.