President Obama's controversial pick to head the Justice Department's Civil Rights Division faces a potentially close -- and for Senate Democratic leaders, embarrassing -- vote Wednesday in the chamber.

The nomination of Debo Adegbile is at risk despite a move in November by Senate Majority Leader Harry Reid, D-Nev., to change the chamber's rules to make it easier to overcome Republican filibusters and confirm White House nominations.

Adegbile has been widely praised by the legal community and liberal groups, who consider him one of the nation's preeminent civil rights lawyers.

But Republicans and at least one Democrat oppose Adegbile because of his involvement in the legal representation of Mumia Abu-Jamal, a black nationalist who was convicted in 1982 of murdering Philadelphia Police Officer Daniel Faulkner.

The issue stirs up a more-than-30-year-long debate over Abu-Jamal, who opponents say is a cold-blooded cop killer. His worldwide supporters, however, say he was wrongfully convicted, with some claiming he was framed by the police because is was black.

Adegbile, as part of the NAACP Legal Defense Fund, helped commute Abu-Jamal's death sentence to life in prison in 2011, a move opponents say makes Adegbile unfit to serve in the Justice Department.

"I believe he is too deeply committed to a host of liberal causes to be an effective leader of that office," Sen. Chuck Grassley of Iowa, the senior Republican on the Senate Judiciary Committee, said at a February meeting of the panel.

Supporters of Adegbile, currently senior counsel for Senate Judiciary Committee Chairman Patrick Leahy, D-Vt., say he was upholding a centuries-old American tradition of affording all suspected criminals legal representation, no matter the crime.

"Lawyers have an ethical obligation to uphold that principle," said American Bar Association President James R. Silkenat in a January letter to the Senate Judiciary Committee.

Adegbile's "work, like the work of ABA members who provide thousands of hours of pro bono legal services every year, is consistent with the finest tradition of this country's legal profession and should be commended, not condemned."

Members of the Supreme Court Bar, in a letter to the committee, also noted that conservative-leaning Supreme Court Chief Justice John Roberts earlier in his career represented a Florida death row inmate convicted in the murder of eight people.

But Sen. Pat Toomey, R-Pa., said Abu-Jamal already had multiple attorneys, and that joining the case was a "political cause" for Adegbile.

"As part of this cause, the lawyers supervised by Adegbile promoted the myth that Abu-Jamal was an innocent man who was framed because of his race," Toomey said in an opinion piece published Monday in the Philadelphia Inquirer.

"Thanks in part to the efforts of Adegbile, today Mumia Abu-Jamal is alive and off of death row."

Pennsylvania's Democratic senator, Bob Casey, issued a statement Friday saying that he, like Toomey, won't support Adegbile's nomination.

"The vicious murder of Officer Faulkner in the line of duty and the events that followed in the 30 years since his death have left open wounds for [widow] Maureen Faulkner and her family as well as the city of Philadelphia," Casey said. "After carefully considering this nomination and having met with both Mr. Adegbile as well as the Fraternal Order of Police, I will not vote to confirm the nominee."

Adegbile's nomination requires a simple majority in the 100-seat Senate to pass. But with Democrats controlling only 55 of the Senate's 100 seats, and with every Republican expected to oppose Adegbile, Democratic leaders pushing the nomination have little room for error.

And there is speculation that moderate Democrats in tough re-election fights this year, including Sens. Mark Pryor of Arkansas, Kay Hagan of North Carolina, Mary Landrieu of Louisiana, and Mark Begich of Alaska, will be tempted to buck the president and oppose Adegbile.

The Senate Judiciary Committee in February approved Adegbile’s nomination along a straight party-line vote, 10-8.

The Justice Department's Civil Rights Division, part of the Civil Rights Act of 1957, enforces federal statutes prohibiting discrimination on the basis of race, color, sex, disability, religion, familial status and national origin.

The Congressional Black Caucus is pressing the Senate to confirm Adegbile, saying he has been "under an unwarranted attack."

“Throughout his career, Mr. Adegbile has had an unwavering commitment to justice and integrity," CBC Chairwoman Marcia Fudge, D-Ohio, said Tuesday. "His work ethic has earned the respect of those within the civil rights community and from colleagues who have argued cases with and against him."

But senators are getting pressure from law enforcement groups and Faulkner's widow to oppose the nomination.

"Mr. Adegbile was a willing and enthusiastic accomplice in Mumia Abu-Jamal’s bid to cheat us of the justice we waited so many years for," Maureen Faulkner said in a February letter to senators. "Mr. Adegbile freely chose to throw the weight of his organization behind Mumia Abu-Jamal, and he has publically [sic] stated that he would get Mumia Abu-Jamal off death row."

Some conservatives also worry that Adegbile, if confirmed, would impose a national mandate that would make it tougher for employers to reject job applicants who are convicted felons.

Aside from the Abu-Jamal case, Grassley said he has other significant concerns about Adegbile. Grassley said he is soft on gun rights, was evasive when asked about the legality of voter ID laws, and hasn't been forthcoming when asked if he would commit to implementing recommendations made by the Justice Department's Inspector General regarding hiring in the Civil Rights Division.

"I have no reason to believe he isn’t a man of great personal integrity," Grassley said. "I just don’t believe he is the right nominee to lead this office at this time."