Born and raised in Indianapolis, Indiana, Cantwell graduated from Miami University before moving to Seattle to work on Alan Cranston's 1984 presidential campaign.

Her father, Paul Cantwell,[2] served as county commissioner, city councilor, state legislator, and chief of staff for U.S. Representative Andrew Jacobs Jr.;[2] he was the Democratic nominee for Mayor of Indianapolis in 1979.

[4] After high school, Cantwell attended Miami University in Oxford, Ohio, where she earned her Bachelor of Arts degree in public administration.

After the election, five Democratic representatives from Washington state lost their positions, despite running for re-election, including Cantwell, future governor Jay Inslee, and Speaker of the House Tom Foley.

[23] In 1998, the company was criticized by privacy groups, which alleged that the RealJukebox software program incorporated spyware to track unsuspecting users' listening patterns and download history.

[25] Cantwell entered the campaign a year after Senn, who was endorsed by the Washington State Labor Council and NARAL, and used her personal wealth to fund television advertisements.

[34] Social security, prescription drugs, dams, gun control, and campaign finance reform were among the most important issues in Cantwell's race against Gorton, which drew national attention.

[35] Cantwell also adopted the slogan "Your voice for a change", a veiled reference to Gorton's campaign theme in 1980, challenging incumbent Warren Magnuson's age.

[citation needed] Gorton was endorsed by the smaller The News Tribune and two of the largest Eastern Washington newspapers, The Spokesman-Review and Tri-City Herald.

"Fiddling with people's websites and calling it good fun ... adds a very childish and unworthy character to the race", Senn's campaign spokeswoman Barbara Stenson said.

When RealNetworks stock declined at the end of 2000, she spent time raising funds for debt retirement, but kept her pledge not to accept PAC money.

[46][47] The election result was certified on November 22 with a lead of 1,953 votes for Cantwell out of 2.5 million cast, credited to support from the Puget Sound region.

[50] Cantwell and Debbie Stabenow of Michigan became the third and fourth women to defeat incumbent senators, following Kay Bailey Hutchison's 1993 and Dianne Feinstein's 1992 special-election victories.

Media outlets across the state, including The Olympian and the Yakima Herald-Republic, rebuked her, claiming she was afraid to confront McGavick, calling it "unacceptable"[56] and "simply not fair".

[61][62] In 2005, she wrote a letter in support of the Perkins Loan program,[63] and told the Seattle Times in July 2006 that she opposed Social Security privatization.

Citing his potential views on abortion and the environment, Cantwell was one of 22 senators to vote not to confirm United States Supreme Court nominee John Roberts.

[66] In January 2006, after publicly announcing her opposition to Supreme Court nominee Samuel Alito, Cantwell, 18 other Democrats and all 53 present Republicans, voted for the cloture motion.

[73] She was criticized by her Republican challenger, State Senator Michael Baumgartner, who suggested that she was too extreme and too far to the left of Washington voters on this issue, and expressed concern about 11-year-olds getting these drugs without a prescription.

She also voted against the Unborn Victims of Violence Act, which made it an additional crime to kill or harm a fetus during a criminal assault upon the mother.

Cantwell opposed drilling in the Arctic National Wildlife Refuge (ANWR), and was one of the most vocal critics of the increase of oil and gasoline prices during 2008.

[76] In 2005, Cantwell scored what many perceived as one of the biggest victories of her first term when she blocked Senator Ted Stevens's efforts to allow drilling in ANWR.

[79] She is known for supporting alternative energy research and for protecting Washington's forests from logging and the construction of paved roads and has been endorsed by various prominent environmental advocacy groups.

[84] In 2009, Cantwell introduced the Carbon Limits and Energy for America's Renewal (CLEAR) Act (S. 2877), also called the Cantwell-Collins bill, a "cap and dividend" emissions trading proposal.

[90] One of her main accomplishments was the passage of an amendment "To prevent energy market manipulation", which passed 57–40 in the Senate in November 2006; a previous effort was defeated by a vote of 50–48.

[92] In February 2019, in response to reports that the EPA intended to decide against setting limits for perfluorooctane sulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) in drinking water as part of an upcoming national strategy to manage the chemicals, Cantwell was one of 20 senators to sign a letter to Acting EPA Administrator Andrew R. Wheeler calling on the EPA "to develop enforceable federal drinking water standards for PFOA and PFOS, as well as institute immediate actions to protect the public from contamination from additional per- and polyfluoroalkyl substances (PFAS).

She also complained that jurors had not been sequestered, allowing them to view "negative news coverage" about Knox, and that one of the prosecutors had a misconduct case pending in relation to another trial.

Her October 10, 2002, press release, quotes her as stating on the floor of the U.S. Senate, "Mr. President, my vote for this resolution does not mean that I am convinced of the Administration has answered all the questions.

Cantwell detailed six specific areas in which her questions and concerns had yet to be satisfactorily addressed at the time of her vote to authorize war: "First: Continued Multilateral Approach ... Second: Successful Military Strategy ... Third: A Post-War Commitment Strategy ... Fourth: Fighting the Broader War on Terrorism ... Fifth: Maintaining Middle East Stability ... Sixth: Protecting Iraqi Civilians."

[101] Cantwell supports health care reform in the United States, and was a co-sponsor of Senator Ron Wyden's Healthy Americans Act.

Why doesn't she want Congress to include a public option — a new government-run health-care plan that will be available to everyone, and will compete with private insurance companies to bring down costs — in its health-care-reform package?