Mark Thiessen has some very sharp analysis in WaPo where he traces the roots of the president's troubles all the way back to the stimulus bill and Obama's failure to reach out to a beaten and chastened GOP in order to give the Republicans a stake in it:

Would Republicans have accepted hundreds of billions in new government spending in exchange for including pro-growth tax relief and other GOP proposals? The offer would likely have split the party, with a significant number supporting the bill. The grass-roots movement for fiscal discipline had not yet been born, and many of the same Republicans who voted in favor of the "Bridge to Nowhere" would have gladly compromised with the popular new Democratic president. The stimulus would probably have passed with significant bipartisan support, instead of near-unanimous Republican opposition.

But Obama was not interested in compromise. He decided to go it alone. He picked off a few easy GOP votes and rode roughshod over the rest of the Republicans to pass a maximalist bill over their objections. That may have seemed like a good idea at the time. But looking back now, a week from the midterm elections, the wisdom of his approach is hard to discern.

The stimulus united Republicans for the first time in opposition to the president. It gave rise to the Tea Party movement that has fundamentally transformed the nation's political landscape in the GOP's favor. It changed Obama in the eyes of millions of Americans from the first "post-partisan" president into what many now perceive as (to quote Obama himself) "the same old tax-and-spend liberal Democrat." And his subsequent decision to ram Obamacare through Congress over unanimous Republican opposition sealed this impression, which voters will carry into the voting booth next Tuesday.

Hat Tip: Ed Lasky