Next week, as early as Monday, Senate Democrats will move to vote on a three month extension for unemployment benefits for the 1.3 million people who lost them just after Christmas.

But the chances of passage for the measure are “hanging in the balance,” the Democratic Senator who is taking the lead on rounding up Senate votes for the legislation tells me.

“It’s not determined yet, but we’re going to do everything we can,” Senator Jack Reed of Rhode Island said in an interview. “Hanging in the balance is probably the right way to say it.”

However, Reed sought to project confidence, noting that he thought the bill had “momentum” and vowing to “work straight through” to win over Senators and make it happen.

Reed is co-sponsoring the legislation with GOP Senator Dean Heller, and Reid is lobbying both Republican and Democratic Senators to support the bill, but no GOP Senator other than Heller has publicly come out for it.

Asked whether he had lined up any other Republican Senators to support it, Reed declined to answer directly. “We’re getting people sincerely saying they’re thinking very seriously about this,” Reed said about his GOP colleagues.

Reed noted that a number of GOP Senators represent high unemployment states. If the 55 Dem-aligned Senators vote for an extension, which isn’t assured but is very likely, Dems need five Republicans.

The unemployment rate in Illinois (Senator Mark Kirk’s state) is 8.7 percent; in Tennessee (Bob Corker and Lamar Alexander) it’s 8.1 percent; in Arizona (John McCain and Jeff Flake) it’s 7.9 percent; in Georgia (Saxby Chambliss and Johnny Isakson) it’s 7.7 percent; in Ohio (Rob Portman) it’s 7.4 percent; and in Pennsylvania (Pat Toomey) it’s 7.3 percent. In many of those states, tens of thousands of people have already been cut off, according to stats compiled by Ways and Means Dems.

Reed said many of who have lost benefits are “desperate,” and said he thought other Senators understood this. “Many of them are middle aged, have worked for a long time, and have found that it’s difficult to find jobs,” Reed said.

Fellow Senators, he added, “are sensing back home, through editorials and newspaper stories, that these aren’t people who are enjoying collecting $300 or $400 per week. These are people who worked for decades. The reality is not this hypothetical where everybody will get a job.”

But there’s still no indication Republicans will vote accordingly. As the Atlantic’s Matt O’Brien put it:

Republicans are refusing to extend these extended benefits any longer. They think we have to get benefits “back to normal” even if the economy isn’t — that taking benefits away will give the jobless a needed swift kick in the you-know-what to go get a job…companies won’t even look at the resumés of the long-term unemployed. So the only reason they had to keep searching was to qualify for benefits that required them to. Take those benefits away, and you take those people away from the labor force.

If the measure passes the Senate, that might increase pressure on House Republican leaders to let it pass, though that’s also in doubt. What happens if the measure fails in the Senate? There are several other procedural routes, such as trying to attach the extension to spending bills that will be negotiated later this month.

Before that, though, Senate Majority Leader Harry Reid and Dems have one other tactic at their disposal if it fails. “Senator Reid will reserve the right to vote again — and we’ll keep working,” Reed said.

So you could see a scenario where Dems force Republicans to vote repeatedly against extending a lifeline for tens of thousands their own constituents.