Incumbent Seattle mayor Greg Nickels sought reelection but finished third in the August 18, 2009 primary election.

[6] The Proposed replacement of the Alaskan Way Viaduct and a tax on plastic bags at grocery stores were also major issues of the campaign.

A poll conducted on August 12 showed incumbent Greg Nickels in the lead with 24 percent voter backing.

[2] An October 20 poll commissioned by KING-TV and conducted by SurveyUSA showed Joe Mallahan ahead with 43% to Michael McGinn's 36% with a margin of error of 4.1%.

[14] McGinn changed his position on the Deep Bore Tunnel that same day, claiming "If I'm elected mayor, though I disagree with this decision, it will be my job to uphold and execute this agreement.