Image credit: Josh Reynolds/AP Photo

Another long-serving public official will be hanging up his hat: Boston's longest-serving mayor, Tom Menino, won't seek a sixth term as head of the Bay State's capital city.

Menino, 70, has served Boston as the mayor since 1993, when he ascended to the position after then-Mayor Ray Flynn was appointed as the U.S. Ambassador to the Vatican.

A Democrat, Menino was, and will likely continue to be, a powerful political figure in the state. He famously stayed out of the hotly contested Warren-Brown Senate race last year until September, less than two months out from Election Day, when he endorsed Democrat Elizabeth Warren. His endorsement was seen as a big get for Warren, a backing that was thought to help her with blue-collar Bostonians.

Menino will make a formal announcement about his retirement at 4 p.m. today, but he has already vocalized his decision to local media.

"It was a very difficult decision, when you have something you love, that you live 24/7 for the last 20 years," he told reporters this morning. "It's tough to say, 'No,' but there's a time and a place for everything," he said.