Sen. Claire McCaskill (D-Mo.) said Friday she's two votes short of having enough support to end the Senate's practice of secret holds.

McCaskill said veteran Republican Sen. Richard Lugar (Ind.) had signed onto her letter calling for an end to the long-standing Senate privilege of placing anonymous holds on presidential nominees.

McCaskill broke the news on Friday afternoon via Twitter:

New signature on letter to abolish secret holds. Thank you Sen Dick Lugar. Now we have 65, two more and we have enough to change the rules.

The Missouri centrist has led the push to abolish the process, which gives minority party senators the ability to hold up nominees. Republicans have used the privilege to some effect against President Barack Obama's nominees, most notably senior Sen. Richard Shelby's (R-Ala.) hold earlier this year on 70 of the president's picks for various positions requiring federal confirmation.

The Senate's rules require 67 votes, just over a two-thirds majority, to change the rules. The supermajority requirement is even higher than the 60 votes normally needed to end debate and quash a filibuster.

Sixty-four senators have signed McCaskill's letter, and Senate Majority Leader Harry Reid (D-Nev.) supports it, though he has not signed it because the letter is addressed to him. All other Democrats except Sen. Robert Byrd (D-W.Va.) have signed it. Seven Republicans have also pledged support: Sens. Susan Collins (Maine), Scott Brown (Mass.), Bob Corker (Tenn.), Olympia Snowe (Maine), Judd Gregg (N.H.), Lisa Murkowski (Alaska), and Richard Lugar (Ind.).

Cross-posted to the Twitter Room.