Legislation to beef up investigations into unsolved murders from the civil rights era looked like it would breeze through Congress.

The House passed it 422-2 this summer. Its Senate sponsors included some of the most senior Democrats and Republicans on Capitol Hill.

The bill has stalled since the House vote in June. Its supporters acknowledge that prospects are slim this year with just days left on the legislative calendar. The breakdown offers a case study in how even the most popular legislation can get caught up in Washington gridlock.

“The bill should have passed a long time ago,” said Rita Bender, widow of Michael Schwerner, who was killed in Mississippi in 1964 along with fellow civil rights organizers Andrew Goodman and James Chaney. “Every indication is that if it were brought to the floor and voted on there would be enough votes to pass it.”

The bill is named after Emmett Till, a black teenager who was murdered in Mississippi in 1955 after being accused of whistling at a white woman. His killers were never convicted.

The legislation would authorize $10 million annually over 10 years for the Justice Department to rejuvenate its prosecutions of pre-1970 civil rights murders. It calls for another $3.5 million annually for Justice to provide grants and other help to local law enforcement agencies.

The man most responsible for obstructing the measure is Sen. Tom Coburn, an Oklahoma Republican. Coburn says he supports the cause but feels the FBI can pursue the cases with existing resources.

A spending hawk, Coburn has put a hold on the legislation and dozens of other bills that would increase the federal budget without offsetting costs elsewhere.

“It’s absolutely outrageous that one senator and one senator only appears to be blocking us from passing this piece of legislation,” said Jim Manley, a spokesman for Senate Majority Leader Harry Reid, D-Nev.

Of course, Coburn alone can’t stop the bill. He can only hold it up by forcing time-consuming debate and registering his opposition.

If the measure is so important, he asks, why not bring it to the floor?

So far, Senate leaders have declined to do that. The process could eat up several days and require a series of votes on procedural motions. It also could open the measure to amendments that could weaken the bill.

Senate Democrats say Coburn is blocking about 90 bills, and working around him on all of them would take months — leaving little room for other work.

Coburn’s spokesman, John Hart, acknowledged that Coburn would try to amend the Emmett Till bill by cutting its cost. But if his efforts failed, Hart said, Coburn would simply vote against the bill and let it go.

Hart said no one — including the bill’s Senate sponsor, Chris Dodd, a Connecticut Democrat who is running for president — has personally approached Coburn about a compromise for floor debate.

“It doesn’t make sense for the majority leader to blame a freshman Republican for scheduling problems,” Hart said. “(Coburn’s) intent is not to tie up the Senate for days on this.”

Democrats dismissed the suggestion that they haven’t made the bill a priority. Dodd’s office insisted that he tried to bring it up three times, only to be thwarted by Coburn.

Dodd’s spokeswoman, Justine Sessions, said the bill is “critically important” to the senator and he will “hit the ground running” to pass it early next year if it doesn’t pass before Congress adjourns this month.