Democratic U.S. Sen. Patty Murray's campaign is preparing supporters for a possible tightening of her race against Republican Dino Rossi as more ballots are counted today.

Murray's deputy campaign manager, Alex Glass, said she won't be shocked if Murray falls slightly behind Rossi this afternoon. That's because King County is only expected to count 45,000 ballots, which may be dwarfed by new totals from other counties. (Spokane County alone will count 30,000.)

In a new memo on the state of the race, Jeff Bjornstad, Murray's campaign manager, predicted Rossi will lose even if he appears to surge today.

"The varying rates of counting will likely favor Dino Rossi today as smaller counties - which have received fewer votes and which expect fewer votes to arrive in coming days - are able to more quickly process their backlog. However, the much larger number of ballots yet to be counted in King County - where Patty Murray leads 62% to 38% - means that she will ultimately prevail as counting continues."

"In fact of the 40% of ballots yet to be counted statewide, about 55% are in counties where Murray is ahead or even - King, Snohomish, Whatcom, Jefferson, Grays Harbor, Thurston and Pacific. In counties where Murray leads, there are approximately 523,000 ballots to be counted based on projected turnout vs. 440,000 ballots to be counted in areas where Mr. Rossi leads."

Meanwhile, the Rossi campaign says the race is simply too close to make any predictions.

They've pointed to a statement by Dave Ammons, spokesman for Secretary of State Sam Reed, who told seattlepi.com "both sides have legitimate theories for a path to victory."

Ammons added: "In my view, this is one of those classic too-close-to-call races. We need to let the vote tally continue."

Clearly the key here is King County. If Rossi gains ground there, he has a definite shot. If Murray keeps her 62-38 lead, it's gets impossible for Rossi pretty quick.