GOPers are celebrating and predicting 2010 gains while Dems are largely dismissing the results as unimportant losses based on local factors. I think it's somewhere in between.
As most Democrats point out, these elections aren't always the best indicators of what will happen a year from now. A year is a lifetime in politics. So much can happen with the economy (good and bad), the war on terror, and big issues like health care reform, cap-and-trade and card check. Plus, NJ Democratic Governor Corzine was damaged goods and the Creigh Deeds, the Viriginia Democratic candidate for governor, ran a weak campaign.
But that cannot explain away the decisive results of these two elections. Something was energizing the Republican base, which hasn't happened since 2004. In short, Republicans aren't necessarily inspired to vote for Republicans, but they are getting ticked off at what is happening in Washington. This discontent is translating into higher participation from the GOP base, while loyal Democrats are seemingly uninspired. If this continues, Democrats should be concerned about noticeable losses in 2010.
In Montana, without a big race (I predict Rehberg will do well again) to draw independent voters, the 2010 legislative races will be about which party can get more of their base to show up. In 1998, the last time the U.S. House race was the top race, Montana saw its lowest voter turnout ever. If the GOP base continues to have big concerns about national developments, that may bring more Republicans out to vote in legislative elections while Democrats may be more likely to stay at home.
The question remains, however, if the Republican base will continue to stay energized. Polls show that Republicans don't really even like their own GOP leaders, so gains will have to come from their distaste of the Democratic agenda. If the economy gets worse, that may get more independents out to vote. When it comes to swing voters, it's still the economy, stupid.