Barack Obama has begun his 2012 presidential campaign, and his supporters are starting to make arguments like this, to get you to vote for him (again). These arguments, which point out all the good things he's done, are mostly valid and good reasoning. He got the health care bill passed. He dealt with the Arab Spring well enough that we didn't see anyone over there burning American flags. He nominated two qualified women to the Supreme Court. He got rid of Don't Ask, Don't Tell, and he passed a decent jobs bill. While his role in some of these things can be debated, as can the effect of his economic actions, I think few Democrats believe that they made a mistake in electing him, given the alternative. But we're disappointed because we think he didn't do enough.
During the 2008 primary season, I remember seeing Obama as an excellent speaker: he can make you agree with him without saying anything of substance. The most resonating messages were of hope and change, which worked because it allowed his supporters to fill in the specifics. He did have a platform, but you had to go looking for it, on his website or in the debates, which most people (maybe not you and I) wouldn't do. So it's not as if he didn't keep his campaign promises, it's that he never made them, at least not the ones we thought he did. His campaign set him up for disappointment, and now it has to work that much harder to earn the next four years.
He did do a lot of good, and a few of his priorities were set aside when the economy came crashing down. And when some members of congress decided to throw a tantrum instead of vote on anything progressive. Besides, there's still a lot he wants to do, if only we'd give him more time. And we probably will. I mean, look at the alternatives. It wouldn't be the worst election in recent history.