Tallahassee, Florida (CNN) Sen. Bill Nelson's already improbable path towards victory in a recount has gotten narrower, with the Democrat suffering a series of setbacks in court and in county election offices across the state.

The drumbeat of relatively bad news for Democrats in Florida has left any chance Nelson had of overtaking Republican Gov. Rick Scott's 12,603 vote lead in a recount as a longshot, at best, with the three-term senator needing to win an overwhelming number of votes in the ongoing manual recount or scoring a series of clear wins in court.

Nelson was handed a consequential loss early on Friday morning when Judge Mark Walker ruled that the guidelines Florida law provides to election canvassing boards as to how to determine voter intent in a manual recount are constitutional.

"The issue in this case is whether the use of these reasonable and neutral rules is constitutional," Walker said. "It is."

The loss came around the same time Walker denied a request for Scott to recuse himself from election matters.

Nelson's lawyer's -- led by top Democratic attorney Marc Elias -- have argued the mere fact that the race went to a manual recount was enough of a win for them, given the number of votes in Democratic leaning counties that remain left to count.

They have kept a particularly close watch on Broward and Palm Beach counties, where election officials have said the number of overvotes -- when a voter selects too many candidates in one race -- and undervotes -- when a voter selects no candidates in one race -- number in the thousands. The manual recount currently underway is only of those ballots, where election officials use guidelines from the state of Florida and their own judgment to determine whether a voter meant to vote to one candidate or another.

In Broward County, the number of over and undervotes was over 30,000 ballots. In Palm Beach County, that number was around 6,000, according to Palm Beach County Supervisor of Elections Susan Bucher.

Those votes now represent the only chance Nelson has to close the gap, and even then, the likelihood is dim.

Broward County elections officials announced on Friday morning that they had completed sorting their over and under votes, and the county's canvassing board was now reviewing the ballots and would announce the decision of those in dispute, meaning the intent of the voter was clearly in question.

Bucher, who testified before Walker's court on Thursday, told the judge that her team would finish the machine recount on the Senate race on Friday and then need three to five hours to complete the hand recount. She said that all could happen at some point on Friday.

Elias tried to project confidence on a call with reporters on Thursday afternoon.

"It has never been our view that there was going to be one silver bullet that was going to change the margin in this race," Elias said, noting that Democrats' strategy has long been that they would need a series of wins in court and with election officials to bring home a win for Nelson.

To date, that hasn't happened.

Nelson's lawyers did score a narrow win on Thursday when Walker ruled voters whose mismatched signatures disqualified their provisional and mail-in ballots and who were "belatedly notified" of the problem have until Saturday at 5 p.m. to correct those signature problems.

But even that victory was muted. Lawyers for Nelson and other Democrats had asked for the ballots in question to be counted with no review of the signatures at all. And even though Elias and others celebrated the ruling, Uzoma Nkwonta, a lawyer for Nelson's campaign in the case, told the judge in the hearing that a ruling that only extended the deadline by a few days -- which is what Walker ordered -- "would probably be insufficient."

Walker also denied a request on Thursday that would have made it easier for Nelson's campaign to reach out to voters who had mismatched signatures on their ballots. The lawyers had asked for the judge to require the Florida Secretary of State to release the names of people whose ballots had not been counted because their signatures did not match ones on file. Walker, quite directly, took a dim view of that argument and rejected it from the bench.

"I am not going to be used by either party," Walker told the lawyers. "That's the kind of gamesmanship that would undermine our democracy further."

And Walker also rejected the Democrats' request to remove the state's deadlines for machine and manual vote recounts on Thursday.

"This Court must be able to craft a remedy with knowledge that it will not prove futile. It cannot do so on this record," Walker wrote. "This Court does not and will not fashion a remedy in the dark."

The hits kept coming on Friday evening, when Walker denied a motion from lawyers for VoteVets Action Fund and a series of Democratic organizations who were seeking to stop the state of Florida from enforcing the vote-by-mail deadline. The suit argued that voters should not be held responsible for the speed of the US Postal Service and their ballots should be treated similar to ballots mailed from overseas, which have a later deadline.

Walker did not agree, meaning Florida's vote-by-mail deadlines will stand and domestic vote by mail ballots received after Election Day will not be counted.

Scott's campaign heralded the decision, arguing that it showed it was "long past time for Bill Nelson to face the facts: this charade is over, Floridians' votes have been counted multiple times, and Rick Scott is the next Senator from Florida."

Some decisions remain for Walker, however, and they could go Nelson's way. VoteVets Action Fund and a series of Democratic organizations urged Walker on Thursday to invalidate Florida law that says domestic mailed ballots must arrive in elections offices by election night. The suit argues that voters should not be held responsible for the speed of the US Postal Service and should be treated similar to overseas mailed ballots, which have a later deadline.

Walker did not indicate on Thursday how he would rule on the matter, but even if he does rule in favor of the Democratic interests on the matter, it is unlikely to be enough vote to close the Nelson's deficit. Supervisor of Elections for Leon County Mark Earley testified during the hearing that the number of domestic mail-in ballots that came in after the deadline this year was 178 in his jurisdiction, which includes Tallahassee. While that number would be larger in more populous counties like Palm Beach, Broward and Miami-Dade, it is highly unlikely to be enough for Nelson.

For Tallahassee Mayor Andrew Gillum, the Democratic candidate for governor in Florida, the path to victory in a recount has closed.

Gillum trails former Rep. Ron DeSantis by over 33,000 votes -- a margin that actually went DeSantis' way by one vote during the machine recount.

Gillum has not conceded and, in a statement on Thursday, indicated he would not get out of the race.

In an interview with Pod Save America published Thursday, Gillum said he was in "fighting shape" in Tallahassee and was looking forward to getting every vote counted.