Will Wilkinson thinks that Obama's cowardice on DADT and marijuana can be explained by the generation gap:

Defending status-quo policy on gays in the military or the drug war is bound to alienate many of Mr Obama's most enthusiastic young supporters. But younger voters are a fickle lot in any case. Their turnout in 2008 was an anomaly. It would be imprudent for Mr Obama and the Democrats to count on an equal showing this fall or in 2012. In contrast, you can be sure the always-reliable 65 and older crowd will show up in droves. The stances that would help Mr Obama consolidate support among especially young or especially liberal voters also risk scaring off older voters and capricious independents, and it's clear which tack the White House is taking. Either way, he may be in trouble.