[7] Galvin won a special election to the open seat in the Massachusetts General Court in 1975, after State Representative Michael Daly departed from office; the race had nine candidates.

Galvin defeated Green-Rainbow Party candidate Jill Stein, a medical doctor and environmental health advocate who ran for Governor in 2002, in the November general election.

The Democratic primary race received relatively little attention or press coverage for most of 2006, but in the last few weeks before election, a controversy over Galvin's refusal to debate his opponent broke into the news with a front-page story in The Boston Sunday Globe.

In November 2017, Boston City Council member Josh Zakim announced that he would run for Secretary of the Commonwealth, challenging fellow-Democrat Galvin in the 2018 election.

[19] An investigation by the US Justice Department found that Galvin, as Massachusetts Secretary of State, had violated the Uniformed and Overseas Citizens Absentee Voting Act.

The Office of the Secretary of the Commonwealth was found to have failed to collect and report data on absentee ballots sent, returned, and cast by overseas citizens and military personnel registered to vote in Massachusetts, as required by the law since amendments in 2002.

[22][23] In September 2021, Massachusetts regulators fined MassMutual $4 million for failing to supervise the trading activity of their employee Keith Gill, a leading player in the GameStop short squeeze which led to hedge funds losing billions.

Following his pursuit of litigation against Gill, it was reported that Galvin was engaging in partisan politics and had opposed bilingual ballots in contravention of the Voting Rights Act.