By Sean Sullivan, Isaac Stanley-Becker, Washington Post–

Florida’s historic recount was thrown once more into uncertainty Thursday when a federal judge ruled that thousands of voters whose ballots were rejected because of issues with their signatures will have two more days to resolve the problems and possibly have their votes counted.

The decision by U.S. District Judge Mark Walker came just hours ahead of the Thursday afternoon deadline for elections officials to complete a manual recount. It is particularly notable in the too-close-to-call Senate race, in which Gov. Rick Scott (R) leads Sen. Bill Nelson (D) by fewer than 13,000 votes.

Walker’s decision affects Floridians who cast their ballots by mail but whose signatures did not match records maintained by state officials. More than 4,000 ballots across 45 counties in Florida were set aside for this reason, he wrote in his opinion. In the other 22 counties, the number is unknown.

While the ruling gives Nelson new hope for chipping away at his deficit, it falls short of the more sweeping decision his lawyers sought and is likely not enough to change the outcome of the race on its own. The order also raises new questions about next steps in the recount in three statewide contests, including the races for governor and agriculture commissioner.

In his ruling, Walker said the plaintiffs had established “irreparable injury” — not only to the Democrat’s electoral prospects but also to the constitutional right of citizens “to cast their ballots and have them counted.”

“Here, potentially thousands of voters have been deprived of the right to cast a legal vote — and have that vote counted — by an untrained canvassing board member based on an arbitrary determination that their respective signatures did not match,” wrote the judge, appointed to the federal bench in 2012 by then-President Barack Obama. “Such a violation of the right to vote cannot be undone. ”

Scott’s campaign is expected to appeal the decision.

The ruling was part of flurry of courtroom activity that could influence the contest, even as local election officials scrambled to meet the Thursday deadline to complete their work.

Election officials in Broward County, a populous Democratic stronghold, maintained that they would meet the 3 p.m. Thursday deadline for completing a machine recount. Officials in Palm Beach County faced problems with the counting machines themselves and have said they can’t guarantee they’ll be done Thursday.

Representatives of the Republican and Democratic parties attended a “walk-through” at the Broward elections office to prepare for the manual recount expected to follow in the Senate race.