Senators Tom Udall, Jeff Merkley and Tom Harkin have announced that their proposal for reforming the Senate rules now has 26 co-sponsors, all Democrats. But they represent a healthy ideological cross-section of the entire caucus.

In addition to Udall, Harkin and Merkley, the resolution is currently co-sponsored by the following senators: Dick Durbin (IL), Amy Klobuchar (MN), Sherrod Brown (OH), Mark Begich (AK), Richard Blumenthal (CT), Kirsten Gillibrand (NY), Jeanne Shaheen (NH), Michael Bennet (CO), Barbara Boxer (CA), Benjamin L. Cardin (MD), Bob Casey (PA), Christopher Coons (DE), Al Franken (MN), Kay Hagan (NC), Frank Lautenberg (NJ), Joe Manchin (WV), Barbara Mikulski (MD), Jay Rockefeller (WV), Debbie Stabenow (MI), Jon Tester (MT), Mark Udall (CO), Mark Warner (VA), and Sheldon Whitehouse (RI).

Warner, Manchin, Tester and Hagan being aboard at this point is pretty solid. And there are others, like Frank Lautenberg, Ron Wyden, Claire McCaskill and others, who have their own rules bills with similar elements. The caucus seems united, although ideology is taking a back seat to seniority, or lack thereof, in this case.

Especially seeing that Ben Nelson’s spokesman seriously walked back his opposition today.

Thompson emails that in fact, Nelson is open to supporting Senator Tom Udall’s filibuster reform plan, which was introduced yesterday, as “a starting point.” He adds that Nelson recognizes that “clearly the Senate is dysfunctional and too often dilatory tactics are used to obstruct it from working for the American people.”

What’s more, Thompson says, Nelson isn’t completely ruling out supporting doing reform by a simple majority, which may be necessary if Dems can’t reach a deal with the GOP. When I asked whether this is something Nelson could support, Thompson told me: “Americans want Congress to work together, so the bipartisan work underway on filibuster reform won’t be helped by saying what he might do if it fails.” [...]

“He also strongly supports open debate and has a clear record voting against obstruction, delay and political gamesmanship,” Thompson continues.

You wouldn’t actually need Nelson for the Constitutional option if you had the rest of the caucus, but even he’s at least somewhat open to it. And there’s nobody in the caucus to his right, really.

I think there’s a general sense that the current Senate rules serve nobody, and that it behooves the majority to make things simpler on non-controversial legislation and nominees, while putting the burden on the minority to hold and sustain a filibuster. Al Franken’s tweak would help in that regard as well.