Senator Susan Collins is a Phi Beta Kappa graduate of St. Lawrence University. She worked for Senator William Cohen from 1975 until 1987, when she became chair of the Maine Commission on Financial Regulation. She served in this position until 1992, when she briefly served as New England regional director of the National Small Business Administration. She was the Republican candidate in the Maine gubernatorial election of 1994, but both she and the Democratic candidate, former Governor Joe Brennan, were defeated by the Independent candidate, Angus King.

In 1996, when Senator William Cohen announced his retirement, Collins announced her Senate candidacy. After a difficult three-way primary, she defeated Democrat Joe Brennan in the general election with 49% of the vote to Brennan's 44%. She was reelected in 2002 over State Senator Chellie Pingree (D), 58%-42%.

Known as one of the most bi-partisan members of the U.S. Senate, Collins has been known to cross party lines on important issues. Her willingness to work with members of the opposing party while formulating policy, as well as her ability to think independently of President Bush has earned her the label of Republican in Name Only (RINO) from conservatives. Collins played an important role during the U.S. Senate's impeachment trial of Bill Clinton when she and fellow Maine Senator Olympia Snowe sponsored a motion that would have allowed the Senate to vote separately on the charges and the remedy. When the motion failed both Snowe and Collins subsequently voted to acquit, believing that while Clinton had broken the law by committing perjury, the charges did not amount to grounds for removal from office.

Collins voted with the majority in favor of the "Iraq War Resolution" authorizing President George W. Bush to go to war against Iraq, on October 10, 2002.

On October 21, 2003, Collins was one of the three Republican Senators to oppose the Partial-Birth Abortion Ban Act and voted with the Senate Democrats. The bill was passed 64-34 and sent to President George W. Bush for his signature and became law on November 5, 2003.

With fellow Maine Senator Olympia Snowe on May 23, 2005, Collins was one of fourteen moderate senators to forge a compromise on the Democrats' use of the judicial filibuster, thus blocking the Republican leadership's attempt to implement the so-called "nuclear option". Under the agreement the Democrats would retain the power to filibuster a Bush judicial nominee only in an "extraordinary circumstance", and the three Bush appellate court nominees (Janice Rogers Brown, Priscilla Owen, and William Pryor) would receive a vote by the full Senate.

She voted against the ban on late-term abortions (so-called "partial-birth abortions"), the restrictions on travel to Cuba, harsher punishments for drug users, and opposed amending the U.S. Constitution to prohibit same-sex marriages. She has taken a more moderate line on taxation and trade, voting against some trade agreements, most recently CAFTA. In 2001 she was one of only four Republicans to vote to limit the reduction in the top tax rate and to increase the amount of tax relief for those at the bottom of the income scale. In 2003 she was the only Republican to vote in favor of spending a portion of the tax cut reserved for upper-income payers on the building of hospitals in rural areas. She has voted against drilling in ANWR and in favor of increasing the average mile-per-gallon requirement for vehicles. In September of 2005, Collins cosponsored a resolution with Senator Patrick Leahy, (D-VT), that disapproved a new rule put in place by the administrator of the Environmental Protection Agency that delisted coal and some other energy sources from the Clean Air Act. The resolution failed by a vote of 47 to 51.

Senator Collins coauthored the Collins-Lieberman intelligence reform legislation, which was signed into law in December, 2004. The law represents the most sweeping changes to our intelligence community in more than 50 years and implements many of the recommendations of the 9/11 Commission.

In October, 2006, President Bush signed into law major port security legislation coauthored by Senator Collins and Senator Patty Murray (D-WA).

The new law includes major provisions to significantly strengthen security at our nation’s ports by establishing improved cargo screening standards, providing incentives to importers to enhance their security measures, requiring the Department of Homeland Security to develop a plan for the resumption of shipping in the event of a terrorist attack, and installing radiation detectors at the 22 largest American ports by the end of 2007.

Senator Collins is a member of The Republican Main Street Partnership and supports stem cell research. She is also a member of The Republican Majority For Choice, Republicans For Choice, The Wish List, Republicans for Environmental Protection, and It's My Party Too.

In February, 2006, TheWhiteHouseProject.org named Susan Collins one of its "8 in '08", a group of eight female politicians who could possibly run for or be elected president in 2008.

In January, 2007, Senator Collins cosponsored a bipartisan, non-binding resolution with John Warner, Norm Coleman, Gordon Smith, and Ben Nelson that showed the Senate's disapproval of the President's plan to send 21,500 more troops to Iraq.

Senator Collins is currently the longest-serving Senator to have never missed a roll call vote.

Since January, 2007, Senator Collins has served as the ranking Republican of the Homeland Security and Governmental Affairs Committee. Collins served as chair of the committee from January, 2003, until she became ranking Republican. Joe Lieberman said in his "opening statement" as chair that the committee had no more productive period than Collins' tenure as chair.

Collins also serves on the Armed Services Committee and the Special Committee on Aging. She is also a co-chair of the Congressional Task Force on Alzheimer’s Disease. Her tenure both as chair and ranking member of the Homeland Security and Governmental Affairs Committee has been noteworthy for her close working relationship with Joe Lieberman. Lieberman was previously the committee's ranking Democrat.