Seattle Transit Blog, the local wonky media outlet for mass transportation issues, says incumbent Mayor Mike McGinn deserves another term:

He has pushed for greater investment on all transit fronts. He initiated a badly needed update to the Transit Master Plan, sought to fund it through a $80 vehicle license fee, and used the TMP to open up the possibility of a Sound Transit 3 package in 2016 rather than 2020 or 2024. He has leveraged Seattle’s voracious appetite for transit to accelerate the entire region.

They are less enthusiastic about others in the pack:

Peter Steinbrueck, in addition to flirting with anti-rail rhetoric, displays strong anti-density instincts, consistently favoring replacement of a big building with a small building, and a small building with empty space. Councilmember Bruce Harrell has a poor density-and-transit voting record on the Council and continues to emphasize cheap and easy car access as a policy objective. We are hopeful that Senator Ed Murray would make a good mayor, but Olympia politics is so far to the right of Seattle that is difficult to discern where he stands on the real fault lines in City politics. He has not yet embraced the aggressively pro-transit and pro-density positions that would move us to abandon an incumbent with whom we agree almost totally.

The question about McGinn, though, is this: Can he implement that transit plan; can he turn those funding concepts into actual light rail tracks, train cars, and stations? He hasn't done it in his first term.