This is a debate that was largely ducked in 2008. Earlier in that primary season, party divisions were mostly obscured in the shared revulsion to eight years of George W. Bush. Later, as the field was winnowed to Hillary Clinton and Obama, the divisions were more about competence than ideology.
The understandable excitement over Obama's eventual victory allowed him to run, and then to govern, as something of a chameleon. This was not a phenomenon, as with Romney, of shifting shape to fit the political circumstance as much as it was of being ideologically elusive and indeterminate enough that voters could fairly read into Obama whatever they chose. He was whatever change they decided to believe in.
If Obama wins re-election, he could have an obvious successor in Vice President Joe Biden.But even if Biden chose to run, he would surely face significant competition for the nomination, if not from Hillary Clinton, then from the next generation of Democrats, among others New York Gov. Andrew Cuomo, Maryland Gov. Martin O'Malley and Virginia Sen. Mark Warner.
More broadly, Obama has not forged a cohesive vision of what it means to be a Democrat that would outlast his tenure. Perhaps that understanding would gel in a second term, but for now the shape of the post-Obama Democratic Party is indistinct.
Even as the right assails Obama for alleged socialist tendencies, liberals have been frustrated throughout his presidency for supposed capitulations, on everything from the public option in health care to the debt ceiling deal to civil liberties shortcuts in the war on terror. Whether Obama wins or loses, those suppressed tensions will inevitably surface in 2016.
All of which suggests that the next election, not this increasingly stale, unenlightening campaign, is the one truly worth watching.