The rejection of Debo Adegbile in a 47-52 vote marks the first time that the Senate has thwarted one of Obama’s nominees since Democrats changed filibuster rules in November — a historic change that was supposed to make it easier for the majority party to move nominations.

Vice President Joe Biden presided over the vote in case he would need to break a tie but that wasn’t necessary. The nomination needed 51 votes to advance and seven Democrats voted against the White House and their leadership.

Adegbile drew opposition and scrutiny from national law enforcement organizations as well as a bipartisan group of senators for his involvement with Mumia Abu-Jamal, who was convicted of killing Philadelphia police officer Daniel Faulkner in 1981. Adegbile previously worked for the NAACP’s Legal Defense Fund, which workedin support of Abu-Jamal’s efforts to overturn his death sentence.

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Obama called the failed vote a “travesty based on wildly unfair character attacks against a good and qualified public servant.”

“Those who voted against his nomination denied the American people an outstanding public servant,” Obama said.

Senate Majority Whip Dick Durbin (D-Ill.) told reporters the White House employed a “full-court press” to get support and that Durbin joined with Sens. Patrick Leahy (D-Vt.) and Amy Klobuchar (D-Minn.) to stump for Adegbile at a recent Democratic caucus lunch.

But it wasn’t enough — and Durbin said the result did not take him by surprise. Sources on Capitol Hill didn’t seem shocked either, with one Democratic aide accusing the White House of leading a “botched” nomination process.

“You could see this coming from a mile away,” the aide said.

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Senate Majority Leader Harry Reid (D-Nev.) said the vote would have been closer, but suggested some senators saw the writing on the wall and declined to take the tough vote in favor of the high-profile nominee.

”Everyone knows how things work around here,” Reid said. “When a number of people saw the vote not going a certain way, things always change.”

Adegbile’s past led both of Pennsylvania’s senators — including Democrat Bob Casey — to oppose the nomination. Republicans spent much of Tuesday afternoon and Wednesday morning on the Senate floor criticizing the assistant AG choice pointedly for his work with Abu-Jamal.

“He decided to join a political cause … and in my view, by doing so he demonstrated his own contempt for — and frankly a willingness to undermine — the criminal justice system of the United States,” said Sen. Pat Toomey (R-Pa.). “I do not believe that Mr. Adegbile’s nomination is consistent with justice for the family of officer Danny Faulkner or for anyone else that cares about the law enforcement community.”

But it wasn’t just the GOP. Along with Casey, Democratic Sens. Joe Manchin of West Virginia, Mark Pryor of Arkansas, Heidi Heitkamp of North Dakota, Joe Donnelly of Indiana, John Walsh of Montana and Chris Coons of Delaware voted to block the nomination.

Majority Leader Harry Reid (D-Nev.) also voted no, which — under Senate rules — allows him to bring the nomination back to the floor at a later time. Durbin said in an interview that the rejection of Adegbile was “truly unfortunate” and that it was up to the nominee on whether he wants another vote on the Senate floor.

Manchin said he made a “conscientious decision” after having a “long conversation” with the slain police officer’s widow. Asked repeatedly to elaborate, Machin would only say: “I made a very conscientious decision based on the facts that were put before me.”

Coons said in a statement that Wednesday’s vote “was one of the most difficult” he has taken in the Senate and said his opposition was based not on Adegbile’s qualifications, but instead mostly represented his constituents’ concerns, given Delaware’s close proximity to Philadelphia.

Sen. Tom Carper (D-Del.) said as a matter of principle he votes to advance the president’s nominees past procedural hurdles, and didn’t say whether he would have voted for Adegbile on final passage. But he chided senators for not breaking the filibuster on Adegbile.

“The president’s nominees, especially in this administration, deserves an up or down vote. I just wish more of my colleagues felt that way,” Carper said.

Landrieu, a vulnerable Democrat up for reelection this year in Louisiana, declined to comment on her vote for the nominee as she entered a party lunch. Several other vulnerable Democrats, including Sens. Kay Hagan of North Carolina and Mark Begich of Alaska, also supported the nomination.

Pryor and Walsh are the only two Democrats to oppose Adegbile that are up for reelection this fall — but most of the others who voted “no” surely did so to insulate themselves from political attacks in future years.

The GOP most likely would have blocked the high-profile Obama nominee before Democrats changed the Senate rules on Nov. 21, 2013, to lower the voting threshold needed to clear a filibuster on most presidential nominees from 60 votes to a simple majority. Obama announced his intent to nominate Adegbile to the assistant AG post on Nov. 14.

Senate Minority Leader Mitch McConnell (R-Ky.) said Adegbile’s rejection on Wednesday was evidence that Democrats “have not gained a whole lot” by changing the Senate rules, indicating that it represents a new era of presidential nominees picked with no regard for bipartisanship.

“This particular nominee likely would not have been nominated at all but for the majority leader breaking the rules of the Senate last November to change the rules of the Senate,” McConnell said.

The nomination was also opposed by local Pennsylvania officials as well as national organizations like the Fraternal Order of Police and the National Association of Police Officials, which described Adegbile as someone who “made his name defending one of the most notorious and unrepentant cop killers around.”

A group of 86 organizations, including the AFL-CIO and NAACP, wrote to senators this week urging them to support Adegbile. In the letterthe groups called Adegbile “one of the preeminent civil rights litigators of his generation” and made no mention of Abu-Jamal.

Jennifer Epstein and Seung Min Kim contributed to this report.