Washington uses a nonpartisan primary system in which the top two finishers go to the general election, regardless of party affiliation.  As usual, though, the result will pit a Republican challenger, Dino Rossi, against the Democratic incumbent in the US Senate race, Patty Murray.  The final results aren’t exactly a confidence booster for the incumbent:

Twice-defeated Republican gubernatorial candidate Dino Rossi will face Democratic Sen. Patty Murray in a November contest that could prove critical to GOP chances of winning a Senate majority.

Murray finished first in Washington state’s unique top-two primary, capturing 46 percent of the vote with 60 percent of precincts reporting. Rossi came in second with 34 percent, enough to advance to the general election as the GOP nominee. …

Republicans sought to frame the results as a sign of Murray’s weakness in November, when the GOP will need to pick off several Democratic incumbents from blue states like Washington if the party expects to win control of the Senate.

“As the final results are tallied, the fact that an 18-year incumbent from a blue state who serves as a member of Senate leadership is struggling to get above 50 percent in an open primary speaks volumes about the current political environment in Washington State, and it speaks volumes about the opportunity that Republicans have this November with Dino Rossi as our party’s nominee for the U.S. Senate,” said National Republican Senatorial Committee Chairman John Cornyn (R-Texas) in a statement Tuesday evening.

Murray faced no serious opposition from inside her own party, and yet could not get more than the combined votes of Rossi and Clint Didier.  Didier, who received an endorsement from Sarah Palin but couldn’t generate any upward momentum, got 12% of the vote in the primary yesterday.

The incumbent’s inability to get to 50% looks like a harbinger of the race in November.  Three weeks ago, Rasmussen surveyed likely voters in Washington and found nearly a dead heat.  Murray led Rossi at the time 49/47, with Rossi taking 51% of independent voters.  Both Rossi and Murray have wide name recognition, and they also have similar favorability numbers (52/44 for Rossi, 51/44 for Murray).  This looks like it will be a squeaker, just as Rossi’s two campaigns for governor turned into nailbiters, one of which Rossi only lost after a controversial recount.

The normal indicators also suggest a photo finish.  In liberal Washington, Barack Obama gets a 50/49 approval rating, suggesting that he may not be as much of a factor as in other Senate races.  Governor Christine Gregoire’s approval is underwater at 46/54, which could hurt Murray and suggest that perhaps voters may regret not voting for Rossi in 2008.  The real key may be the perception of the economy; even in relatively comfortable Washington, 44% of voters think their personal finances are worse, as compared to 19% who say better.  If Rossi sticks to the economy in his campaign, he may get enough mileage out of the current stagnation to push Murray out of DC.

One other thing to monitor in West Coast elections will be the impact of races in the East.  If it starts looking like a Republican avalanche early in the evening, it may depress the later Democratic vote in the West.  In Washington, it could be close enough for that to matter.