In the first term of the Obama administration, a big healthcare bill was passed while the Waxman-Markey climate change bill, otherwise known as ACES, sputtered out.
I read an article in my Energy Policy class by Theda Skocpol that had an interesting hypothesis about why the climate change bill didn't pass.
Naming the Problem: What It Will Take to Counter Extremism and Engage Americans in the Fight against Global Warming
According to the article, it's not because there's only enough political capital for one policy (see page 19) nor is it because there was not enough support from the White House (see page 18). Instead, one major difference between the campaigns for ACES and Obamacare is that the proponents for the climate bill focused more on insider bargaining and media ads while a coalition outside the beltway was formed for healthcare known as HCAN (see pages 42 - 46). The new coalition engaged interest groups outside of the beltway and influenced law-making. HCAN formed the bridge between the Democratic DC insiders and the progressives further to the left outside DC ("liberal elite" + "hippies"). In contrast, efforts by cap and trade proponents are characterized by one-way communications from DC to the public (see page 47).