From Pew:
The Republican Party's prospects for the midterm elections look much better than they did four years ago at this time, while the Democrats' look much worse. Voter preferences for the upcoming congressional elections remain closely divided (45% support the Democratic candidate or lean Democratic, while 44% favor the Republican or lean Republican). In polling conducted in August-September 2006, the Democrats held an 11-point advantage (50% to 39%).
What's interesting is where the problem lies (details here):
The GOP is also now running better than four years ago among three key swing groups in recent elections -- independents, white Catholics and seniors.
While the generic looks decent enough (Dems +1 at 45-44), the better likely voter turnout for the GOP means losses for Democrats.
Further, this emphasizes once again, the problem isn't so much the base, it's the indies.
Republicans and Democrats express near-unanimous support for candidates of their own party (93% each), while independents are divided (42% for Republican candidates vs. 35% for Democratic candidates).
More than eight-in-ten Republican-leaning independents (85%) favor the GOP candidate in their district; 78% of Democratic-leaning independents support the Democratic candidate.
Is it rational? Well, never underestimate what voters don't know. Separately, Pew publishes this:
Only a third of Americans (34%) correctly say the Troubled Asset Relief Program (TARP) was enacted by the Bush administration. Nearly half (47%) incorrectly believe TARP was passed under President Obama. Another 19% admit they do not know which president signed the bank bailout into law. Notably, there is no partisan divide on the question. Just 36% of Republicans, 35% of independents and 34% of Democrats know that the government bailout of banks and financial institutions was signed into law by former President Bush. And Democrats (46%) are just as likely as Republicans (50%) to say TARP was passed under Obama.
In fact, the public knows a lot more about Twitter than TARP. But they do know about economic conditions, and they will vote on that.