The economy is in relative shambles, and the Republicans were extremely unpopular in 08 whereas Obama was the utter reverse. As economic woes persist, as the 8 horrible years of Bush become less proximate, as nervousness ensues over the new president's agenda, it is inevitable that the Democrats will loose some of their present power because basically they got about as much power through the 06 and 08 elections as it was possible for Democrats to acquire with the electorate. This isn't to say they'll lose their majorities in both houses, but these majorities are likely to decrease. More certainly in the house than in the senate because the third of the senate that is coming up for reelection next year was last elected in 04, which was the last time the republicans did well in a federal election. In contrast, the entire house is up for reelection every year, so the Republicans are very likely to gain some seats in the house. The only third parties that have ever succeeded, and only a few ever did, in the 200+ years history of the US democracy were vast defections from a preexisting major party. Through a combination of largely lacking run off elections and of as a rule having winner takes all elections for legislatures (as opposed to the proportional system that exists in many European states and ensures minority voices gain representation thereby removing the risks associated with voting for a third party) the US system ensures a duopoly on power. Hence, although the American people are dissatisfied with both parties, they are tragically stuck with them.