This is actually a good argument for a California/Washington style system for mayoral elections in cities where the Democratic primary is all that matters. It sucks for statewide elections but it is more representative and democratic in one-party municipalities. Minneapolis basically used such a system before switching to IRV. Fenty probably would've won a basically non-partisan open to all voters runoff.
That's the way municipal elections in Washington have been for a while, even before the state switched. Though the state still lists party.
