Snowe, the first woman to serve in both chambers of her state legislature as well as both chambers of the U.S. Congress, cited Capitol Hill's "atmosphere of polarization" to explain why she has decided not to run for re-election. A search in Sunlight's Capitol Words of the terms she uses most often on the floor of the Senate highlights her record as an advocate for her constituents and women's health. Among Snowe's favorites: Maine, fisheries, dairy, fisheries, ocean and breast. The senator was eight years old when she lost her mother to breast cancer, and has been a leading advocate for research on the disease. Her profile on Sunlight's Influence Explorer shows that the biggest earmark she requested -- $138 million -- was for breast cancer research. Next biggest: $80 million for prostate cancer research.

By comparison, Sen. Jon Kyl, R-Ariz., -- first elected to the Senate in 1994 with Snowe and, like her, retiring this year -- favors words like "treaties," "nuclear," "Russians," and "weapons." His biggest earmark requests, according to Influence Explorer: $25 million for a civic education program and $20 million for a ballistic missile defense terminal.

Kiely is the managing editor of the Sunlight Foundation, a non-profit and nonpartisan organization that promotes government transparency.