Thomas Joseph O'Connor Jr. (July 27, 1925 – September 11, 1996) was an American politician who served as mayor of Springfield, Massachusetts.

[1] In 1957, O'Connor swept all 68 of the city's precincts to defeated 12-year incumbent Daniel B. Brunton for the Democratic nomination for mayor of Springfield.

[1] During his tenure as Mayor, O'Connor oversaw a downtown road system and urban renewal project that received $3 million in federal funds.

[3] On June 15, 1960, O'Connor announced he would challenge Governor Foster Furcolo for the Democratic nomination for United States Senate seat held by Leverett Saltonstall.

[13] On October 11, 1960, 4,500 residents attended a meeting at Springfield Auditorium where members of the Board of Assessors attempted to explain the tax increase.

Each member was booed off the stage before they could speak and O'Connor, who had no role in the property reassessment, failed to quiet the crowd and police were called in.

[14] O'Connor planned to cut 578 jobs from the 1961 budget in order to reduce the city's taxes, however he reversed this decision due to a lack of public support.

[17] Two weeks after O'Connor's loss, the city's percentage assessment system, which had been a major issue during the campaign, was declared unconstitutional by the Massachusetts Supreme Judicial Court.

[20] In 1990, Hampden County District Attorney Matthew J. Ryan, Jr. retired and O'Connor, his longtime friend, was seen as his favored successor.

Bennett, the more conservative candidate, was able to attract the majority of financial contributors and campaign volunteers, as well as endorsement from former federal prosecutors, Ryan's former assistants, and Judd Carhart, the president of the state district attorneys' association.