David Costello, who challenged U.S. Sen. Angus King in 2024, is officially the third Democrat vying to oust Republican Sen. Susan Collins in this year’s high-profile midterm elections.
An Old Town native and former government official in both Maine and Maryland, Costello qualified for the June 9 Democratic primary by submitting more than 2,000 signatures before the Monday deadline, according to his campaign and Secretary of State Shenna Bellows’ office.
Costello, who now lives in Brunswick, enters as a longshot in the race with Democratic Gov. Janet Mills and progressive oyster farmer Graham Platner, whose race is getting national attention. Costello had 4% of support in a survey released earlier this month showing Platner 7 points ahead of Mills.
Collins and Republicans in several states aim to fend off a push from Democrats to retake control of at least one chamber of Congress and blunt President Donald Trump’s agenda.
Costello’s campaign website cites working-class roots and more than 30 years in government and leadership roles. He previously served as a top aide to Maine’s secretary of state, the Baltimore mayor and Maryland governor. He was also deputy secretary and acting secretary of the Maryland environmental protection department and regional team leader for the U.S. Agency for International Development.
As he did two years ago, Costello says he’s running on a progressive “reform agenda.” He calls for eliminating the Electoral College, campaign finance overhauls, and shaking up Capitol Hill by expanding the House and restructuring the Senate according to state populations.
He also supports codifying abortion protections in Roe v. Wade, universal pre-kindergarten and after-school care, and expansions to federal food, health and education programs.
In 2002, Costello was one of six Democrats in a primary for Maine’s 2nd District, a race won by Mike Michaud. In the 2024 race in which King won a third term, Costello picked up almost 11% of the vote compared with 52% for King, an independent, and roughly 35% for Republican Demi Kouzounas.
Costello was the best-known candidate who was likely to join the U.S. Senate by the 5 p.m. deadline. All of the major gubernatorial hopefuls had qualified for the ballot as of Friday.
