-- Special election overreaction: Since they are all we've got at any particular point in time, observers have a tendency to overreact to the results of House special elections. A victory by either side won't augur much of anything for the fall campaign. No matter who wins, national Democrats and Republicans will weigh tonight's results against their expectations and polling and try to figure out which elements of the campaign worked in their favor. Both sides are confident that the focal points of the campaign (preventing changes to Social Security and Medicare for the Democrats, and connecting local Democrats to President Obama and Nancy Pelosi for the GOP) can be applied with success elsewhere; indeed, they already have. So, later on this cycle, both sides will apply lessons they learned in the final matchup between a Democrat and a Republican before November.
But in the end, the district is a testing ground, not a fulcrum for a national momentum shift in either direction. The local details surrounding any House race make blanket projections to the national level a difficult exercise, and this is no exception. In the short term, the only tangible national result from the special election is which side of the House of Representatives the winner joins.