imo, the situation in America and the world at large will still be atrocious when the 2010 midterms roll through. With that in mind, I think the Democratic Party would be very unwise to abandon the "change" theme next year. Sure, the Democrats have the White House and Congress; but the Republicans can easily prevent reform from being enacted. The GOP is virtually certain to campaign on some kind of "change/reform" platform in 2010, but we should steal their issue from them.
The Democratic slogan in 2010 should be "Had Enough?" A simply effective classic, and the target would be Republican obstructionism. Obama's personality would be kept
out of the campaign at this level; he would, however, make solemn (and very public) pleas for bipartisanship, implying there are "good" Republicans who want to rise above party lines for the good of their country. Around this time, Democratic pundits should begin to drop the term "Obama Republican" at any given opportunity- the more public attention (even "legitimacy") given to these voters, more of them will be "created."
Finally, and most importantly, the Democrats need to pick one single, tangible issue with heavy public support to advance... and contrive to
lose the fight. The vote, of course, will be mostly party-line. After that, they can flood the airwaves- especially in states and districts that voted for Obama- with "Had Enough?"
Think it could work?