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In another sign that the U.S. Senate is racing the clock to the end of the year and adjusting to life under a new set of rules, senators confirmed one of President Obama's picks to serve on a key federal court, acting in the middle of the night Thursday amid Republican objections to changes in Senate procedural rules.

Shortly before 1 a.m. Thursday, the Senate confirmed Cornelia "Nina" Pillard 51 to 44 to serve on the U.S. Court of Appeals for the District of Columbia Circuit. Pillard will be the second of three picks by Obama to join what many legal experts consider the second-most-important federal court in the nation because it handles cases regarding federal regulations.

But three moderate Democratic senators -- Joe Donnelly (Ind.), Joe Manchin III (W. Va.) and Mark Pryor (Ark.) -- voted with 41 Republican senators against Pillard amid concerns among conservatives about her views on abortion rights and the Constitution.

A Supreme Court scholar at Georgetown University, Pillard has argued dozens of cases before the Supreme Court and other federal courts. She will be the fifth active female judge on the D.C. Circuit, a record high.

Obama acknowledged Pillard's historic appointment in a statement early Thursday, noting that she defended the constitutionality of the Family and Medical Leave Act before the Supreme Court. "I'm confident she will be a diligent, thoughtful and judicious addition to the D.C. Circuit," Obama said.

Five senators did not cast votes on the Pillard nomination early Thursday.

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Around 9 a.m. senators confirmed Chai Rachel Feldblum, one of Obama's picks to serve on the Equal Employment Opportunity Commission, and later Elizabeth Wolford, to serve as a federal district court judge in Buffalo.

The votes are happening at odd hours as Republicans continue objecting to the decision by Democrats last month to change Senate procedure regarding the confirmation of most executive branch and judicial nominees. Republicans warned when Democrats voted to change the rules that they would use all other procedural tactics at their disposal to slow the consideration of nominees, including declining to yield back hours of time set aside for each nominee, as historically has been the practice.

Later Thursday and into Friday, senators will continue with procedural and final confirmation votes on three nominees to serve on U.S. district courts in Montana and New Hampshire; on Deborah Lee James to serve as secretary of the Air Force; Heather Higginbottom to serve as the deputy secretary of state for management; and Anne Patterson, to serve as an assistant secretary of state for Near Eastern Affairs.

At some point Friday, the Senate will begin debating the nomination of Jeh C. Johnson to serve as the next Homeland Security secretary. Aides said the Senate likely would break overnight Friday and return Saturday afternoon for a final vote on Johnson's confirmation.

The Senate will then return next week to finish up work on budget and defense policy bills and possibly other nominees, aides said.

Updated 11:13 a.m.