Longtime Republican Senator Susan Collins had held the seat for nearly three decades, but was swept away in the blue wave.

Democrat Troy Jackson, a former Maine Senate president and labour organiser who entered the race in July, has won the Senate race in Maine, flipping a seat held by the Republicans for 30 years.

Longtime Republican Senator Susan Collins conceded the race to Jackson early on Wednesday, ending nearly three decades as Senator for Maine.

Maine’s race was one of the most closely watched in the country. Republican groups spent heavily on the race, donating $76m compared with $40m by Democrats. Jackson’s campaign raised $26.9m, slightly more than the $25.2m for Collins through mid-October.

Located in the far northeastern United States bordering Canada, Maine’s economy has been affected by Trump’s tariff wars with its northern neighbour and key trading partner.

Collins, who has served as senator since 1997, has framed herself as sharing voters’ moderate politics and serving the state’s 1.4 million residents as chair of the Senate’s powerful Appropriations Committee.

Polls released shortly before the election suggested Jackson edging out Collins in a tight race shaped by negative campaigning.

Collins distanced herself from Trump during the campaign but drew criticism for voting in favour of Trump’s legislation and judicial nominees after the Supreme Court ended abortion rights.

Jackson, who campaigned on strengthening the economy and government accountability, framed Collins as a Trump ally and accused her of corruption, which she has denied.

Collins focused on her independence – she was one of the few Republicans who voted to remove Trump from office after the January 6, 2021 attack on the Capitol – and attacked Jackson for his federal inexperience and his voting record in the state legislature.