In 2004 the Bush campaign famously took a rival's positive -- John Kerry's military career -- and turned it into a negative. This cycle the Obama campaign has succeeded in the arguably more difficult task of turning a negative into a positive. From the Wall Street Journal:

The latest Wall Street Journal/NBC News poll shows that, when asked who would better handle the issue of taxes -- the one area where the Republican nominee once had an edge -- 48% said Sen. Barack Obama, and 34% said McCain. Earlier this month the candidates were tied on the issue and just a month ago McCain was leading.

Obama's decision to emphasize his middle class tax cuts in the debates took head-on what voters typically perceive as a losing argument for Democrats. As with foreign policy, his campaign has shown a willingness to tackle issues Dems normally shy away from; they've done so with the confidence that they can convince the American people they have the better side of the debate. Now after weeks of hearing the arguments on both sides voters are saying, loud and clear: I am not Joe the Plumber.