A good point from Adam Nagourney at the NYT:
Ronald Reagan’s average job approval rating in the months before his first mid-term Congressional election, in 1982, was 42 percent — and Republicans that November lost 26 seats. And who remembers that? Two years later, Reagan carried 49 states as he galloped to a second term over Walter F. Mondale.Though, this does not mean that Obama will turn things around. It means it's not written in stone that he can't. On the present course, I remain skeptical that things will get better for the White House. I don't see them trying to mend relations with the Democratic base, and I don't see the president showing a lot of decisiveness on health care reform or Aghanistan, among other issues. The anger, disappointment and disillusionment that a growing number of Democrats have with the President, the Congress and the party will continue to make things worse for Democrats over time, I fear.