Which is why GOP obstructionism in this case is such a curious strategy. The Republican Party has gone "all in" on the hope/belief that the economy will not perk up any time soon. They're even running television commercials bragging about how not a single House Republican voted yea. They have positioned themselves in such a way as the country's interests and the Republican Party's interests are now wholly incompatible. Should the economy not recover, the GOP can run on "we were right, you were wrong". But should things start to improve, the Republicans will be cemented as the "party of no". That - combined with having misplayed two straight really big hands (Iraq) - will surely give the Democrats a Congressional plurality so great that it would leave the Republicans as nothing more than an insignificant fringe party. Their very brand would be trash for a generation, until they emerge, re-invented, several election cycles down the line.
There are two forces at work that the President clearly underestimated here.
First, he drew up a bill that was way too bipartisan to start with. He didn't make the Republicans fight for the tax cuts that are a part of the package, depriving them of the ability to take home some semblance of a win, which would have allowed them to get behind the bill. Remember: politics, not principles. You don't win back any power by finding points of agreement- you do it by wholesale differentiation. Obama would have been smarter to have drawn up a recovery plan with all spending, no tax cuts, then let the GOP fight to include tax cuts in the package. They would have taken home enough of a win to satisfy the ideologues that they made the Democrats come back to the middle. But instead, Obama started in the middle, so with nothing to fight for, Boehner and Cantor and the extremists on the right (including McCain in the Senate) now claim this was not a bipartisan bill - a unique bit of revisionist history given where the bill started and the extensive consultations with the Republican caucuses. Unfortunately, since the bill started off in the middle, the only way the GOP could extract a win would be a bill that was fully a Republican creation.
The other phenomenon Obama underestimated - and while he probably understands it, he will have a tougher time overcoming it - is that the Democrats and Republicans do not merely differ on points of policy. The two parties are fundamentally, culturally wired in different ways. The only loose, guiding principle of the Democrats is a desire for progress, and the willingness to use the apparatus of the government to help spur that progress when needed. The Republicans, however, have hardened their platform into a full-on secular religion. One Republican, shortly after the election, even couched his comments on desiring to work with the new President in religious terms, speaking of a desire to help to "show him the way"... as if defeating the scourge of liberalism is missionary work, driving Satan from our hearts and minds.
For the Republicans, there is one true way, and moral clarity is expendable in the name of winning in much the same way the devoutly religious throughout history have been able to justify ill-treatment of their fellow man in the name of a mandate from a higher place. Whatever level taxes are at now, they should be lower. Period. Government should be smaller and intervene less. Period. The free market should rule. Period. Personal responsibility can be relied upon as a matter of public policy. Period. And then there's the quagmire of the culture war.
There are no guiding principles, meant to be applied strategically and judiciously according to circumstance. The Conservative/neocon movement is not a starting point for negotiation, and it's not even about doing what's best for the country. It's a dogma to be fought for. Mitt Romney said as much when he withdrew from the Republican primary - a rare moment of honest candor from someone more often prone to dissemination of, well, bullshit.
Democratic rhetoric is about making things better in this country. And if you, as a conservative, want to have an intellectually honest debate about just how involved the government should be in that process and what may constitute inefficiency and overreaching, we can have that discussion. But most Republican rhetoric and policy and strategy today is about fighting for their side, for Conservative principles. If conquering the country for Conservative principles helps the country... well, that's the natural side effect of the triumph of the one true way, in their eyes. But it's that one true way, not the side effect, that they are fighting for.
If this obstructionist gambit doesn't work, it will be the equivalent of the Hiroshima bomb going off over the GOP. They will be flattened by it, not to be heard from again for a decade or two.