A lot of people here on the Kos and members of the punditocracy have talked about how the eventual Democratic Presidential candidate will go up against Bush, and if they will bring out the Democratic base, appeal to swing voters, etc. Mostly questions about the electorate and the voters in general.
But the Presidential candidate affects not just who votes for them, but the party infrastructure itself. Usually, the Presidential candidate gets to choose the head of the DNC or RNC and their lieutenants and ultimately decides what direction the party itself will take.
So my question is this: what Presidential candidate will most positively affect the Democratic Party? Please post your reasons below.