Tomorrow the Senate will vote on whether to allow the same simple anti-escalation resolution that passed the House today to go to the Senate floor -- but a key adviser to Dem Senate leader Harry Reid says that Dems probably don't have the votes to make this happen.

Reid spokesman Jim Manley tells Election Central that he thinks cloture will garner a Senate vote in the low to mid 50s -- well short of the magic number of 60. Upshot: The Senate may end up failing to do what the House did today -- that is, to have a straight yes-or-no vote on whether it supports escalation. It would be the second time in a row that the Senate has failed to bring a vote on the "surge" to the floor.

"It's difficult to imagine that we're going to get the 60 votes necessary to block a Republican filibuster," Manley says. "But we're hoping to get as strong a majority as possible."

Dems need 11 Republicans to join with them to reach 60. Election Central today was only able to confirm that four GOP Senators -- Olympia Snowe, Susan Collins, John Warner and Gordon Smith -- will vote to allow the resolution to go to the floor.

Asked if he was simply trying to lower expectations in advance of the vote, Manley said that his reading was a straightforward one. "They've clearly decided they can take a hit from the headlines and not pay long term damage," he said.

Of course, Dem leaders may be calculating that there's an upside in losing tomorrow -- because it gives them more ammo to paint Republicans as too fearful to debate escalation in the Senate.

As one source close to Reid puts it, "After these guys cast the vote, they're gonna have to go back to their home states and justify their votes. It's a politically perilous place for them to be. They're saying the Senate shouldn't even have this debate. I think that's an untenable position."

Meanwhile, a source in GOP Senate Minority Leader Mitch McConnell's office tells us that he too is confident that Dems don't have the vote to pass the measure.

Tune in tomorrow...