Neither side wins with their base alone. Both need the middle to swing their way.
Elections don't swing the middle. The middle swings elections.
This is MoveOn.org's fundamental flaw. You don't change an electorate's mind during an election cycle. You get somebody elected and then he shifts the nation thourhg competent leadership.
Reagan shifted the nation right, but only after his election. They didn't elect him because he convinced them to be more conservative. They elected him because he wasn't Carter and then, during his eight years, the country shifted to be closer to him.
Bad governance shifts the electorate too. Bush is pushing the country leftward.
You don't shift the center during an election. You put up a candidate who is closer (or who can appear to be closer) to the center than your opponent. Then, if he governs well, the electorate will become comfortable with that candidate's politics and shift.
The wingnuts of the GOP got away with putting up conservative candidates and winning mostly because the Democrats ran a series of utterly incompetent campaigns. Bill Clinton is the only competent Presidential candidate the Democrats have had since JFK got shot. So it was easy to throw out conservatives and get them elected. And slowly, the country shifted rightward.
In the Democratic Party the middle is running the show which is why they come across as so wishy-washy.
When the Middle ran the show, Clinton got elected. Twice. Gore lost when he ran away from the middle. Kerry lost because he was such an incompetent campaigner he couldn't describe his own positions coherently.
The Democrats need competent centrist candidates. They have a unique opportunity this election, not merely because they have Bush, but because all of the GOP candidates appear to be as inept campaigning as the Democrats usually are.
All the talk about Hillary hate and "Will America elect a black man" is smoke and mirrors.
Here's an analogy. in American baseball, we spend the season worrying about fielding, batting and coaching. But once you get to the playoffs, one rule wipes that out: the team with the better bullpen will win.
In American politics we worry about all sorts of nonsense, and trivial late-night comedy fodder. But when it comes to the election only two things matter: Did you run a competent campaign? and Do you appear to be more centrist than your opponent?