All Senate Democrats returning to Congress next year have signed a letter to Senate Majority Leader Harry Reid asking him to take up filibuster reform first thing in the new year.

It's a sign that the Republicans' use of the filibuster at historically high rates to block Democratic legislation may have backfired, and coalesced the political capital needed to change Senate rules.

The letter, delivered this week, "expresses general frustration with what Democrats consider unprecedented obstruction and asks Reid to take steps to end those abuses," the National Journal reports.

Among the chief revisions that Democrats say will likely be offered: Senators could not initiate a filibuster of a bill before it reaches the floor unless they first muster 40 votes for it, and they would have to remain on the floor to sustain it. That is a change from current rules, which require the majority leader to file a cloture motion to overcome an anonymous objection to a motion to proceed, and then wait 30 hours for a vote on it.

"There have been more filibusters since 2006 than the total between 1920 and 1980," Sen. Tom Udall (D-NM) says.

Udall has proposed a plan that would allow Democrats, who will hold 51 seats in the new Senate, to change the rules using a simple majority. Currently, Senate rules require that a change to the rules, such as a change to filibusters, be agreed to by an even larger super-majority -- 67 votes -- than the 60 needed to overcome a filibuster.

But Udall says this is unconstitutional, because the Constitution allows each new Senate to change its own rules. Udall's "Constitutional Option" would see rule changes made with 51 votes -- just enough for the Senate to change filibuster rules, if Democratic senators' unanimity on the issue holds. (An 1892 Supreme Court ruling agrees with Udall's argument.)

Changing filibuster rules is not without historical precedent. In 1917, the bar for a filibuster was set at 67 votes, and in 1975 it was reduced to 60.

Another proposal, put forward by Sen. Tom Harkin (D-IA), would see the threshold for a filibuster fall as the filibuster goes on.

"On the first cloture attempt, sixty votes would be required. But, over a period of days or weeks, the number of votes required would fall to a simple majority of fifty-one senators," he wrote in The Nation.

Regardless of the specific shape of the filibuster reform -- which could come before the Senate as early as Jan. 5 -- the very push to change the rules shows that the GOP tactic of heavily using filibusters may have backfired, Ezra Klein argues at the Washington Post.

"They say elections have consequences. So too, it turns out, does obstruction," he writes. If the Democrats don't lose their nerve, the Republican minority will soon "labor under the knowledge that misuse of the rules will mean reform of the rules."

The push to change filibuster rules isn't limited to the halls of Congress. A coalition of progressive organizations has come together to form Fix the Senate Now, a pressure group meant to support the effort to reform Senate rules. Among the organizations backing Fix the Senate Now are the AFL-CIO, the Brennan Center for Justice, Common Cause, SEIU, the Sierra Club and United Steelworkers.

"In the US Senate, there are back room deals, secret holds, and filibuster rules that allow a handful of senators to stop the rest from making any progress. Senators don’t even get to debate about really important legislation on the Senate floor, let alone vote, and no one is held accountable. But the rules can be changed by a majority vote at the start of the next Congress," the group implores.

Conservative observers have accused the group of "astroturfing" the filibuster reform movement.

And as the effort to change the filibuster gains steam, Republican backers -- afraid of a loss of influence in the upper chamber -- have begun to argue that no reform is necessary.

"The bottom line is this: the Senate was never intended to be a democratic body, a reflection of one man, one vote," writes "Vladimir" at the Red State blog. "It is a deliberative body, and a consensus-building body. The filibuster has an important role to play in making that possible."