WASHINGTON — For the third time in as many weeks, Republicans in the Senate blocked a vote on one of President Obama’s nominees to the U.S. Court of Appeals for the District of Columbia, spurring Democrats to renew their threat to change long-standing filibuster rules.

As expected, the Senate voted largely along party lines, 53 to 38, to end debate on the nomination of Robert L. Wilkins, currently a U.S. district judge, falling short of the 60 votes needed to proceed to a confirmation vote.

Last week, in a similar vote, Republicans blocked the nomination of Cornelia “Nina” Pillard, a Georgetown law professor. Patricia Millett, a Washington attorney who worked in the Office of the Solicitor General, was blocked on Oct. 31.

Caitlin Joan Halligan, another Obama nominee, withdrew from consideration in March after Republicans voted against her nomination for a second time.

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Senate Majority Leader Harry Reid (D-Nev.), speaking before Monday’s vote, slammed Republicans for rejecting another “exceedingly capable nominee” for what he characterized as “blatantly political reasons.”

“Republicans have blocked these nominees solely to deny President Obama his constitutional right to appoint judges,” Reid said, calling it a violation of an earlier bipartisan agreement to only block nominations in “extraordinary circumstances.”

“No senator has questioned the character, ethics or qualifications of the three women that have already been rejected for the D.C. Circuit,” he said. “No one has questioned the character, ethics or qualifications of Judge Wilkins.”

In May the Senate confirmed Srikanth Srinivasan to the D.C. Circuit Court, the first such confirmation in seven years to what is considered the second-highest court in the nation.

Obama named Wilkins, Pillard and Millett for the three remaining open seats in June, leading Republicans to accuse him attempting to appoint more liberals to a panel that is currently evenly divided between Democratic and Republican appointees.

Republicans accused Democrats of having used similar tactics to deny President George W. Bush the ability to fill the same vacancies in his second term. They accused the Democratic majority of engaging in a “political exercise” on judicial nominations to distract from issues with the new healthcare law.

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“There is no crisis on the D.C. Circuit, because they don’t have enough work to do as it is,” said Sen. Charles E. Grassley (R-Iowa), the top Republican on the Judiciary Committee. “But there is a crisis occurring right now all across this country as a result of Obamacare.”

Sen. Mitch McConnell (R-Ky.), the minority leader, said Democrats should instead focus on calling votes for nominees to other federal courts around the country, where vacancies are classified as “judicial emergencies” due to the heavy workload.

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michael.memoli@latimes.com

Twitter: @mikememoli