Horse-race polls will get more interesting in September when voters pay increased attention. In evaluating the Party's preparedness for a full-scale campaign, the Dems overall political image looks very good. Pollster.com's Mark Blumenthal reports, for example, that a new Diageo-Hotline survey shows a generic Dem candidate leads a generic GOP candidate 47%-29% in a white house '08 matchup.

Blumenthal's link-rich article also provides some instructive insights about how generic candidate polls work, along with this thoughtful appraisal of their limitations:

...This far out, I believe that a generic vote question tells us mostly about the way voters perceive the national political parties. While those images apparently give the Democrats a huge early advantage - a finding that is certainly informative about the voters' current attitudes - the ultimate nominees of each party and their campaign messages will likely reshape those images. So, for my money, the generic vote remains something of questionable value in tracking where the race will be in 18 months.

Very true about the limited predictive value, and same goes for candidate horse-race polls this far out. But any poll that gives Dems an 18 percent advantage with voters is welcome news in assessing the Party's image, which needs to be strong if Dems want an '08 sweep. Now it would be interesting to see polls showing which themes are resonating with those who prefer a generic Democrat and which motivate those favoring Republicans.