The Dems do need the youth vote. As Pew has pointed out, despite some slippage, young people overall still provided the generous cushion by which Obama beat Romney. Romney, like McCain before him, actually won voters 30 and over. In some important ways, then, the battle for the presidency may well be the battle for younger voters.

If Obama has lost support among younger voters, it seems likely that Clinton will also struggle to maintain a connection with them as a presidential campaign gets underway. To the extent she is a known quantity to younger voters, it’s as Obama’s secretary of state—the face of a foreign policy that is simultaneously a self-evident failure and one that simply wasn’t bellicose enough for Clinton’s tastes.

Either way, that’s no way to win the youth vote; neither is her generally uncritical support of a national-security state and her use of Edward Snowden as a “punching bag.” Assuming that the GOP nominee is someone around the ages of Christie or Paul, she’ll also be about 15 years older than her opponent, which flips the age-party relationship of the past two elections as well. And the Democrats’ problems only get bigger if Clinton doesn’t run: They’ve got virtually no other obvious ready-to-go candidates in the wings.