John Dickerson of Slate described the whys and wherefores well enough:
That's it in a nutshell. Moving forward, those of us favoring both jobs and Obama's re-election (remind me why again?) are, let's face it, expecting the main effect to be, after the Republicans reject the jobs plan out of hand, that it will strengthen the president's hand, that is if he demonstrates enough backbone to carry the gambit out to the end. That and the benefit of the Republicans nominating a basket case and/or nutjob for their candidate in 2012.
Obama no doubt strengthened his base by putting Republicans on the spot. He also suggested he wouldn't abandon the fight as he has before, when, after a strong speech, he flees the ring. "This plan is the right thing to do right now," he said. "You should pass it. And I intend to take that message to every corner of the country."
Liberals such as Paul Krugman liked the proposals on policy grounds, arguing that its incentives for hiring will provide a large return on the investment. The president made a case to the broader electorate that he's leading on the issue they care about. Will he be able to make Republicans pay for obstructionism if his program or some modification doesn't pass? He'll have to make good on his promise to campaign across the land, and he'll have to lay blame and point fingers.
That won't be enough to win him re-election, however. If the political strategists are right and the natural tendency is for this election to be a referendum on the incumbent, then the president will have to work to overcome that. He'll have to give people an affirmative reason to vote, rather than simply stay home out of frustration. That's a pretty grim prospect that he can only hope will be improved by the GOP nominating a terrible candidate.
How did we get here? Stop the parade, I wanna get off.