The U.S. Senate voted overcome a threatened filibuster on an extension of unemployment benefits Tuesday morning, a result considered unthinkable even 24 hours earlier and a rare reminder that politics isn't always a predictable business. But, the vote might mean less than meets the eye.

This Dec. 19, 2013 file photo shows the shadow of the Capitol Dome cast onto the Senate side of Capitol Hill in Washington. A world-famous symbol of democracy is going under cover, as workers start a two-year, $60 million renovation of the U.S. Capitol dome. AP Photo/Susan Walsh, File

The vote -- 60 yes votes, 37 no  votes -- stunned a political world that had expected the unemployment insurance vote to be yet another log on the partisan-polarization-equals-gridlock fire. (Sorry, we are into bad heat metaphors since its in the single digits in Washington today.) Heritage Action, a leading outside conservative group, said Monday that the vote would be a 
key vote -- meaning it would factor into how lawmakers were rated by the organization. Nevada Sen. Dean Heller, a sponsor of the legislation and as of this morning the lone Republican publicly supporting it, felt compelled to take to the Senate floor Monday night to defend his conservative bona fides.

And yet, it passed with six Republican senators -- Kelly Ayotte (N.H.), Susan Collins (Maine), Dan Coats (Ind.), Heller, Lisa Murkowski (Alaska) and Rob Portman (Ohio) voting with a united Democratic caucus in support of ending debate on the measure.  Ayotte, Collins and Murkowski are centrists who tend to be swing votes. Heller's support is directly attributed to the high unemployment rate in his state. In statements after the vote, Portman and Coats explained that they simply wanted the measure to be debated and amended -- in hopes it could be improved upon before final passage.

That's a critical point to understand.  This was a vote to start debate on the measure, not to pass the legislation. The 60 votes simply mean that the terms of debate on the measure will now be established and, Republicans hope, a series of amendments will be allowed to be offered.  "If Majority Leader Reid once again obstructs Senate Republicans from offering amendments, [Senator] Coats will oppose final passage of the bill because he believes any further extension should be paid for by eliminating duplicative and wasteful government programs, many of which have been identified by the administration and the Government Accountability Office," said Coats spokeswoman Tara DiJulio.

In short, today's vote in the Senate sets up the possibility of a negotiated deal -- it is not a negotiated deal in and of itself. A second filibuster threat looms, and if some of those six Republicans who voted "yes" Tuesday switch their votes, it will come up short of the necessary 60-vote threshold.

Then there is the Republican-controlled House, which in the wake of the Senate vote insisted that no extension of unemployment insurance benefits will be approved unless a way to pay for the cost of doing so is embedded in the legislation.

"One month ago I personally told the White House that another extension of temporary emergency unemployment benefits should not only be paid for but include something to help put people back to work," House Speaker John Boehner (R-Ohio) said in a statement. "To date, the president has offered no such plan. If he does, I’ll be happy to discuss it, but right now the House is going to remain focused on growing the economy and giving America’s unemployed the independence that only comes from finding a good job.”

Was this Senate vote a surprise? Absolutely. Was it an encouraging sign for Senate Democrats and the White House? Yes. Does it mean the extension of unemployment insurance is likely? Still, no.