Updated April 3, 2018 -- A milestone is looming during a busy election season in Suffolk County. State Rep. Nick Collins will be unopposed in the April 3 Democratic primary as he seeks to fill a vacancy in the First Suffolk Senate seat.

The Tuesday election has Collins alone on the ballot, next to a write-in option, and the Republican and Libertarian slots will be write-ins. Polls open at 7 a.m. for the district, which includes broad swaths of South Boston, Dorchester and Mattapan.

While Collins will need to face off with unenrolled candidates Althea Garrison and Donald Osgood, Sr. on the May 1 final election, the South Boston representative enters the primary in strong shape. He has some $160,000 in his war chest and the endorsements of politicians including former state Sen. Linda Dorcena Forry, state Rep. Dan Hunt, and most recently Suffolk County Sheriff Steven Tompkins.

Several have already pulled papers for the general election race later this year for the First Suffolk: Collins, Osgood, Duckens Petit-Maitre (D), and unenrolled candidates Garrison, Jesus Rosa, and Elciana M. Ogunjobi. Garrison, however, announced at a Reporter-moderated panel that she plans to run for the First Suffolk only in the special election, and instead run in the fall for the Fifth Suffolk seat, which she represented for one term in the 1990s.

Meanwhile, the field to replace Dan Conley as Suffolk District Attorney widens still further. Lawyer Linda Champion pulled papers on March 9 to seek the post, after Conley announced last month that he would not run for re-election.

Champion is the fifth Democrat openly seeking the seat: state Rep. Evandro Carvalho, of Dorchester, who is an attorney and a former prosecutor in Conley’s office; Greg Henning, of Dorchester, who led the Suffolk district attorney’s office gang unit and has worked in the office for about a decade; and Shannon McAuliffe, of the North End, who was director of Chelsea-based Roca, which works with gang-involved youth; and Rachael Rollins, of Roxbury, former chief legal council for Massport and former Assistant US Attorney.

Boston City Councillor At-Large Michael Flaherty, of South Boston, announced Monday night that he would not seek the seat.

"While I have long been interested in the DA’s position, and greatly enjoyed my time spent as a prosecutor, I will always put my home life ahead of career interests," he said in a statement. "We have been working through a family medical matter and, while the prognosis is good, my full attention is on what is most important to me, my family. Now is not the right time for me to take on the immense obligations of a countywide campaign."

Mayor Martin Walsh’s chief legal counsel Eugene O’Flaherty, of Charlestown is reportedly still mulling a run.

Candidates for all state and district races have until May 1 to file nomination papers.

Henning turned in over 1,600 signatures at City Hall in mid-March, his campaign said. Carvalho this week touted endorsements from state Reps Jay Livingstone of Beacon Hill, Liz Malia of Jamaica Plain, Mike Moran of Brighton, Jeffrey Sanchez of Jamaica Plain, and Chynah Tyler of Roxbury a week after former US Attorney for Massachusetts, Wayne A. Budd, was announced as Carvalho’s campaign chair.

In the Fifth Suffolk state representative district, up for grabs after Carvalho decided to seek the district attorney post, seven interested parties have pulled nomination papers, though not all are still hoping to claim the seat.

Community activist Elizabeth Miranda jumped into the race on March 22. Darrin D’Wayne Howell, a Dorchester resident and former staffer for then-City Councillor Chuck Turner and a political organizer at the 1199SEIU healthcare workers union, pulled papers on March 12, according to the Secretary of the Commonwealth’s office. Howell sought the Sixth Suffolk seat, won by state Rep. Russell Holmes, in 2010. In an interview with the Boston Globe in March 2017, Howell said he may seek elected office again.

Other names in contention for the Fifth Suffolk include Democrats Brad Howze, and Roy Owens, and unenrolled candidates Garrison and Steven A. Wise. Ceferina Murrell, former chief of staff for state Sen. Forry, initially pulled papers to run, but confirmed on Tuesday she would no longer be running.

State Rep. Dan Hunt, running unopposed for his 13th Suffolk seat, has submitted some signatures already, according to the Secretary of the Commonwealth’s office. State Rep. Russell Holmes is also presently unopposed in his re-election bid for the Sixth Suffolk rep’s seat. Only one person— Ryan McGoff—has so far pulled papers to fill Collins’ open Fourth Suffolk seat in South Boston and parts of Dorchester.

In the 12th Suffolk House district, representing Mattapan and parts of Dorchester and Milton, incumbent state Rep. Dan Cullinane may face a second challenge from Jovan Lacet, who has pulled papers for the House seat. Cullinane faced Lacet in 2016, winning the race and defending his seat in 2016 with 54 percent of the vote to Lacet’s 34 percent.