She served as a member of the Vermont Senate from Windham County from 2015 to 2023, as majority leader from 2017 to 2021, and as president pro tempore from 2021 to 2023.

She moved to Vermont in 1994, and worked as a teacher, rock-climbing instructor, and columnist for the Brattleboro Reformer, and was active in local politics.

She was selected to serve as majority leader and later elected president pro tempore, the first woman and openly LGBT person to do so in Vermont.

[3] In the sixth grade, she admitted to having a crush on a female classmate, for which other students taunted her, including writing "lezzie" on her locker; she came out to her friends after high school[3] and to her parents while she was in college.

[3][9][10][11] She met Elizabeth Wohl in 2000; they formed a civil union in 2004, moved to Brattleboro in 2007, and got married in 2009, after same-sex marriage was legalized in Vermont.

[13] She raised the most money in the race, around $13,000, with donations from people such as Jane Lynch, and was endorsed by Majority Leader Philip Baruth.

[23] In 2020, the Democratic caucus selected her to succeed Tim Ashe as president pro tempore of the Vermont Senate, and she became the first woman and openly LGBT person to serve in the role.

[34] During the 2020 Democratic presidential primaries she and other members of the Vermont General Assembly declined to endorse any candidate for president.

[36] Peter Welch, the member of the United States House of Representatives from Vermont's at-large congressional district, announced that he would run to replace Leahy.

She was selected to replace David Cicilline on the United States House Committee on the Judiciary in June 2023, after his resignation.

[60] She supported legislation that sent all voters mail-in ballots and said that it was a part of Vermont's legacy of making voting easier.

[64][65] In 2021, an amendment to the Constitution of Vermont to codify Roe v. Wade passed in the state senate, 26 to 4, with Balint in favor.

[71] She supported legislation banning the gay panic defense, which passed unanimously in the state senate, but was unable to vote for it because she was presiding in place of Lieutenant Governor Molly Gray.

[72] In 2024, Balint wrote an opinion column on MSNBC criticizing Speaker Mike Johnson and congressional Republicans for banning incoming Representative Sarah McBride, the first openly transgender member of Congress, from using women's or gender-neutral restrooms in the Capitol.

"[76] On November 9, hundreds of protestors marched on a fundraiser hosted by Balint, demanding that she call for a ceasefire in the 2023 Israel-Hamas War.