Senate Republicans blocked another one of President Obama's nominees for the D.C. Circuit Court Tuesday, prompting speculation about whether Democrats will try to change the Senate's filibuster rules.

The Senate voted 56-41 in a procedural vote on the nomination of Nina Pillard to be a U.S. Circuit Judge for the D.C. Circuit Court, falling four votes shy of the 60 needed to pass. Today's vote is the latest in Republican's attempts to block Obama's judicial nominees.

Pillard joins Caitlin Halligan and Patricia Millett on the list of nominees to the D.C. Circuit Court that Republicans have shot down this year. Last month, Senate Republicans also blocked the confirmation of Rep. Mel Watt, D-N.C., to head the Federal Housing Finance Agency.

Senate Democrats were infuriated by the latest block and argued that a rules change should be considered.

"I think we're at the point where there will have to be a rules change," Sen. Patrick Leahy, D-Vt., chairman of the Senate Judiciary Committee, said in a news conference after the vote.

"I think it's a turning point for this body because I think it will necessarily involve us to re-examine these rules," Sen. Richard Blumenthal, D-Conn., said. "What the outcome will be, whether we press forward with the rules change or not, the imperative is there."

Senate rules currently require 60 votes in order to close debate on a bill or nominee. Republicans and Democrats brawled over the summer when Senate Majority Leader Harry Reid threatened to employ the "nuclear option," which would have changed Senate rules with a simple majority of 51 votes rather than the 67 currently needed. The two sides eventually came to an agreement that kept Senate rules intact and avoided the "nuclear option."

But Leahy argued Tuesday that the Republicans who helped avert a major change in the rules this summer are now needlessly filibustering nominees who are completely qualified.

"We had a lot of Republicans who said that time there should be only a filibuster in the most extraordinary circumstance. Each one of those Republicans who said that have filibustered this time on this," Leahy said, slamming his hand on the podium. "Their credibility is shred."