The Seattle Times has a roundup of presidential campaign activity in Washington state, which often - with its relatively late March 6 caucuses - isn't a big factor in presidential nominations. If the battle for the nomination is still alive then, though, Washington could be a hotbed.
In some ways, it's a national mirror. The highest-ranking Republican official to take a major role with one of the campaigns, 5th District Representative Cathy McMorris Rodgers, is a leader of the Mitt Romney effort. (Her brother is also heavily involved.) Electability is a key argument there.
The story notes, "It is [Ron] Paul, however, who may have the deepest grassroots organization. Paul, who has not won in any state, has said he’s focusing his campaign on caucus states such as Washington." And Washington caucuses have some history of veering off to the ideological corners, so there's basis for a serious Paul effort. And he's the one Republican presidential presidential candidate with a campaign office in the state (at Bellevue).
And the other two, Newt Gingrich and Rick Santorum? So far, apparently way behind. Santorum has virtually no activity in the state. Gingrich has a little, but his fundraising has been minor and his major supporter is the periodically controversial Rev. Joe Fuiten, pastor of the evangelical Cedar Park Church in Bothell.