Liberal groups are agitating for another round of filibuster reform, after Senate Majority Leader Harry Reid’s (D-Nev.) controversial triggering of the nuclear option last year has done little to alleviate Senate gridlock.

A coalition of labor and liberal groups have pressed Reid to make additional changes to the Senate rules this year, something that senior Democratic aides say is very possible.

“We strongly urge Majority Leader Reid and Chairman [Patrick] Leahy [D-Vt.] to consider reforms to floor and committee rules that will hasten the confirmation of President Obama’s talented and qualified set of nominees,” they said in a statement.

The coalition, known as Fix the Senate Now, includes Alliance for Justice, the Communications Workers of America, Common Cause and the Sierra Club.

Reid is reluctant to provoke another confrontation with Republican colleagues over the rules, but he’s frustrated with the continued obstruction and needs the help of outside groups to turn out voters in the midterm elections.

“Reid is not afraid to go further and considers reform this year a real possibility,” said a senior Senate Democratic aide.

The Democratic leader has already slammed the door on President Obama’s request to move trade promotion authority legislation, which labor unions detest.