37.6% Romney24.6% Paul23.9% Santorum10.4% Gingrich
Apparently 3.5% of caucus attendees spoke up for other candidates. Google also has an Associated Press map of Washington showing which counties favored which candidate.
This win gives Romney a nice boost going into Super Tuesday three days hence. He now has won roughly 16% of the 1144 delegates necessary to have a majority, according to The New York Times. Santorum, the second highest, has won exactly half as many.