5. Harry Reid
The Democratic majority leader was lauded for his efforts enabling passage of the health care reform bill earlier this year. Now, the party, as well as the White House, will be looking to Reid make climate change legislation a reality. Reid’s ability rally Democrats, especially moderates and those in oil-friendly states, to support the bill will be key in determining its success in the Senate. The question is whether Reid’s impending re-election will influence how hard he’s willing to push a bill if it’s viewed as unpopular.