On the last day mayoral and at-large candidates were able to apply for nomination papers at City Hall, a Savin Hill resident waded into the race, while another Dorchester resident withdrew his name from contention.

Catherine O’Neill, who appeared in an ad last year for Elizabeth Warren’s U.S. Senate campaign, pulled nomination papers to run for at-large on Monday. A Lower Mills native and Savin Hill resident, O’Neill had been serving as campaign manager for state Rep. Linda Dorcena Forry’s Senate run, taking over for Cayce McCabe after he left for District 8 Councillor Michael Ross’s mayoral campaign.

O’Neill is well-known in local political circles and wrote a play based on some of her experiences, titled “Murph.”

Separately, local activist Gene Gorman said on Twitter he is pulling out of the at-large race. “I am pulling the plug on my campaign,” he tweeted on Monday night, before deleting his Twitter account. “Election cycle better spent getting Marty Walsh elected mayor.”

Reached by email, Gorman, who jumped into the race after City Councillor At-Large Felix Arroyo launched a mayoral bid, confirmed that he will not run for City Council At-Large.

Gorman has been involved with the Dorchester Historical Society and Dorchester Youth Soccer.

City Councillors At-Large Ayanna Pressley and Stephen Murphy are running for reelection.

The departures of City Councillor At-Large John Connolly and Arroyo to run for mayor have set off a stampede of hopefuls. Michael Flaherty, a former city councillor at-large from South Boston, is hoping to return to the 13-member council.

Michelle Wu, a former Warren campaign aide, jumped into the at-large race in December.

Aside from Wu, O’Neill, Flaherty and the two incumbents, 21 potential candidates have applied for at-large nomination papers.

Candidates must gather 1,500 certified signatures from registered voters in order to qualify for the ballot. Monday, May 21 at 5 p.m. is the last day and hour for filing nomination papers at City Hall.