Sen. Ed Murray has often voiced a desire to be Mayor, "but not this year." He's never been a fan of Mayor Greg Nickels, particularly peeved over the way the Mayor has remained coy on what the city wants for the Montlake end of the floating bridge, where the 43rd District Democrat is in deep quicksand. So it's not surprising that he'd enjoy a little bubble about his possibly being a write-in candidate for Mayor.
Another factor has been the uncertainty about Referendum 71, the anti-gay-partnership measure which has just passed the signature test and will now be on the November ballot. Murray is a gay legislator, so it's thought he would be helped by having the measure on the ballot, which would draw out more gay and lesbian votes than usual.
The real reason for the boomlet, pushing Murray as a write-in candidate, has been the opportunity for the big-wallet interests in the race, suddenly bereft of Mayor Nickels, to use the Murray possibility as a way to get Joe Mallahan and Mike McGinn to listen up. I suspect that's already been happening, which may be one reason that labor and business interests are now downplaying the Murray prospects. The long-shot nature of the Murray candidacy is easy to see: write-in campaigns rarely work (no name on the ballot); voters tend to feel snookered by the side-door entrant; Murray is not particularly well known citywide, and he has no real issue to run on; and the gay vote is always high-turnout.
Another factor is the realization that a Murray in the race would likely translate into a McGinn in the Mayor's office. Murray would split the pro-tunnel vote with Mallahan, and would take away other centrist voters. A hot, single-issue candidate like McGinn would have a much better chance in a three-corner race, where 40 percent might be enough to elect. Sorry, Ed!