4. Olympia Snowe and Susan Collins
Olympia Snowe and Susan Collins
Last year's rank: 7

As truly moderate Republicans, the Maine senators are an endangered species in Washington these days. They've mostly kept their heads down amidst the rise of the Tea Party. But they remain quiet champions of the increasingly elusive middle ground and could help shape compromises that boost economic growth and tackle the deficit.

Last updated September 29 2011: 3:11 PM ET