WASHINGTON — Sara Gideon, the speaker of the Maine House of Representatives, on Tuesday formally became the Democratic nominee to challenge Senator Susan Collins of Maine, wielding a formidable war chest in a race that could determine whether Republicans retain control of the Senate in November.
Ms. Gideon, backed by the Senate Democratic campaign arm and a number of outside political groups, had long been the favorite to challenge Ms. Collins, the sole remaining New England Republican in Congress. The nonpartisan Cook Political Report has rated the race a tossup, and the election has already become the most expensive in Maine history.
“We launched our campaign just over a year ago & I’m so proud of what we’ve accomplished,” Ms. Gideon said on Twitter before the polls closed. “19 #SupperWithSara events, 11 virtual town halls, countless grassroots events, 1 million calls to Mainers, & so much more. I know that we’ll win this primary & again in November.”
While Ms. Collins coasted to a fourth term in 2014 with 69 percent of the vote, her reputation for independence and bipartisanship has suffered under the Trump administration, and her approval ratings have plummeted at home. Though she has split with President Trump on a number of issues, she faced a significant backlash after supporting the $1.5 trillion tax-cut package in 2017 and voting to confirm Brett M. Kavanaugh to the Supreme Court in 2018.
Millions of dollars have flooded the race and the airwaves in Maine, with Ms. Gideon raising $23 million from both voters in Maine and national Democratic donors eager to flip the seat and secure control of the Senate.
Having defeated two progressives — Betsy Sweet, a lobbyist, and Bre Kidman, a lawyer — Ms. Gideon is set to receive another windfall: at least $3.5 million raised by a crowdfunding campaign during and after the confirmation of Justice Kavanaugh. (Because organizers vowed to return the donations if Ms. Collins voted against his confirmation, the senator has condemned the money as a bribe seeking to influence an official act.)
When Ms. Gideon announced her campaign in June 2019, she said her candidacy was in part influenced by the senator’s decisive vote in Justice Kavanaugh’s confirmation. After Justice Kavanaugh dissented from a decision that would uphold precedent to preserve abortion rights, Ms. Gideon and other advocacy groups that favor abortion rights were quick to renew attacks against Ms. Collins, who is also favors those rights and said she believed Justice Kavanaugh would support the precedent to preserve them.
In interviews this month as she traveled across the state for Fourth of July festivities, Ms. Collins acknowledged that Ms. Gideon’s war chest, coupled with the restrictions imposed by the coronavirus pandemic, had made the race particularly challenging. Her campaign schedule has been limited to virtual meetings and fund-raisers and the few remaining outdoor events.
“That’s what’s frustrating to me in this pandemic, because I can do this in a rural area, at an outside event, but the vast majority of fairs and festivals in our state have been canceled,” Ms. Collins said. “I think that’s a huge loss for me, because people know that I’m there because I want to be there, and it energizes me.”