A spot-on NY Times column from Paul Krugman about what the Democratic candidates should be doing, namely running against Bush. It's all worth reading, but the end is worth repeating:
The irony is that by seeking to undermine the election prospects of a man who may well be their party's nominee, Mr. Lieberman and Mr. Kerry have reminded us of why their once-promising campaigns imploded. Most Democrats feel, with justification, that we're facing a national crisis -- that the right, ruthlessly exploiting 9/11, is making a grab for total political dominance. The party's rank and file want a candidate who is running, as the Dean slogan puts it, to take our country back. This is no time for a candidate who is running just because he thinks he deserves to be president.
http://www.nytimes.com/2004/01/02/opinion/02KRUG.html