John Sides argues convincingly in the LA Times that once the Democratic nomination race is finished, the dynamics of an Obama-McCain campaign are very likely to unify Democratic voters around Obama. It’s a good piece, and a welcome reminder that it would be good to see more political scientists doing popular writing on these much-discussed points about election dynamics.
I’d say that the more legitimate concern about unity would have to do with elite unity. There’s a certain set of people who, say, donated to the Clinton re-election campaign in 1996, to Al Gore in 2000, to the DNC when Terry McAuliffe was chair, to some pro-Kerry 527 groups in 2004, and to Hillary Clinton’s primary campaign in 2008. These folks aren’t going to vote for McCain, but how invested will they be in backing Obama? That’s in part going to be a function of whether or not Bill and Hillary urge them to be deeply invested in backing Obama. And much the same could be said for other brands of elites — interest group leaders, random consultants and strategists, etc.
Maybe Hillary Clinton would strongly prefer being Vice President to being Senator from New York. If so, her sway over these kinds of people could be a good reason for Obama to seriously consider a unity ticket even though such a ticket has a bunch of other drawbacks.