For months, the race for mayor of New York City has felt stuck in suspended animation. Not anymore.

The contest was expected to lurch into motion on Sunday with a new front-runner: former Gov. Andrew M. Cuomo. He, Mayor Eric Adams and seven fellow Democrats will face off in a four-month fight to Primary Day.

Fresh off announcing his candidacy, Mr. Cuomo, 67, planned a burst of activity to reintroduce himself to New Yorkers and show the range of his appeal. Among other events, he was expected to pick up his first labor endorsement as a candidate at a rally with the carpenters’ union in Lower Manhattan.

The events marked Mr. Cuomo’s first experience as a bona fide candidate since 2018, and the start of a bid to convince voters to give him a second chance after he resigned the governorship in 2021 amid accusations of sexual harassment. Mr. Cuomo has denied wrongdoing, but his opponents are determined to remind voters of the scandal.

His comeback attempt was met with immediate blowback from political forces as diverse as women’s rights organizations and The New York Post. The right-leaning tabloid slammed him on Saturday as “colossus of canards, a freak of fabrication, a behemoth of balderdash,” while the other candidates argued he had failed New York City as governor.

A left-leaning super PAC was already engaged to stop Mr. Cuomo, an avowed moderate. The group, New Yorkers for Better Leadership, held a call on Saturday to highlight stains on Mr. Cuomo’s record, including criticism from a woman who lost her mother at a nursing home during the pandemic and blamed Mr. Cuomo’s leadership.

Lauren Hitt, a spokeswoman for the group, said that Mr. Cuomo had worsened problems like subway delays and street homelessness.