Jay Cost explains why Obama wasn’t able to do more:

In our system, it’s not just the number of votes that matter, but – thanks to Roger Sherman – how they are distributed across the several states. Obama’s urban support base was sufficient for political success in the House, which passed a very liberal health care bill last November. But rural places have greater sway in the Senate – and Obama’s weakness in rural America made for a half-dozen skittish Democrats who represent strong McCain states. The evolving thinking on the left – “Obama should have used his campaign-trail magic to change the political dynamic” – is thus totally misguided. The “remarkable capacities he displayed during the 2008 campaign” never persuaded the constituents of the red state Democrats he had to win over. Why should they suddenly start doing so now?

Obama simply lacked the broad appeal to guide the House’s liberal proposal through the Senate. So, the result of “going big” was an initially liberal House product that then had to be watered down to win over red state Senators like Landrieu, Lincoln, Nelson, and Pryor. The end result was a compromise bill that, frankly, nobody really liked. Liberals were disappointed, tantalized as they were by the initial House product. Conservatives were wholly turned off, recognizing as they did that the guts of the bill were still liberal. And Independents and soft partisans were disgusted by congressional sausage-making and wary of the bill’s provisions.