Nate Silver nails it:
To channel my Inner Krugman: it's a political imperative for the Democrats of the highest order to get some sort of jobs bill to Obama's desk -- the sooner and the bigger the better. Suppose you could create jobs at a price of about $40,000 per, which is higher than the figure suggested by empirical research on highly targeted jobs programs. A $200 billion bill would then create 5 million new jobs, which would reduce unemployment by about 3.3 percent (e.g. from 10.2 percent to 6.9 percent).
Everything the president wants to do is being pulled down by anxiety around unemployment. His argument would be that reforming healthcare is essential to bringing those jobs back and easing the burden on small businesses in particular, which is true, but the American people ain't feeling that right now. They just want a job, man.