Shenna Bellows, a leading candidate to replace Graham Platner as the Democratic nominee in Maine’s marquee Senate race, dropped out Sunday, as another candidate, Troy Jackson, gained momentum in a delegate selection process crucial to determining the new candidate.
Ms. Bellows said in a statement that “the best way that I can serve our state and country at this moment is by focusing” on her role as Maine’s secretary of state. She left the race as Mr. Jackson, a progressive former state lawmaker, was solidifying his advantage among delegates elected to vote on Mr. Platner’s replacement at a convention next week.
The Democratic nominee who emerges from that convention will face Senator Susan Collins, a vulnerable fifth-term Republican incumbent, in the November midterm election. The race in Maine is considered central to Democrats’ chances of winning back the Senate.
“The most important thing we can do in this moment is unite to defeat Susan Collins,” Ms. Bellows wrote on social media, adding in her statement that “Democrats don’t have a day to waste.” She did not immediately endorse another candidate.
Her bid ended 11 days after Mr. Platner suspended his campaign following an allegation of rape that he has denied. Ms. Bellows ran against Ms. Collins in 2014 and lost by 37 percentage points. Earlier this year, she came in fourth in the Democratic primary for Maine governor.
Democrats in Maine have spent the weekend gathering at county meetings where they have been selecting 500 delegates who will join about 100 members of a state party committee in voting on the nominee at the convention next week.
At those meetings, a large share of the delegates selected have been voters who say they support Mr. Jackson, according to a review of county results, campaign delegate slates and interviews with Democratic operatives. County meetings for all 16 Maine counties were expected to be completed on Sunday.
In a gusty parking lot outside a performing arts center on Sunday, Mr. Jackson gave a speech to his supporters before the York County delegate vote kicked off.
“Yesterday, we showed them what this movement can do, what your movement can do,” he said. “Today, York County gets that chance. Let’s elect this slate, let’s win this nomination, and let’s unite this party.”
In a social-media post after Ms. Bellows withdrew, Mr. Jackson wrote, “Thank you, Shenna, for your friendship, your service to Maine, and your dedication to our shared values.”
“Defeating Susan Collins will take all of us, and I’m grateful for your commitment to bringing Democrats together around that mission,” he added.
Another candidate, Jordan Wood, who lost in a competitive House primary last month, also responded swiftly, writing on social media that he was inspired by Ms. Bellows. “Proud to call you a friend,” he added.
In a debate last week, Ms. Bellows acknowledged that she was rushing to study up on Ms. Collins’s recent voting record. When a debate moderator corrected her about Ms. Collins’s position on U.S. military action in Venezuela, Ms. Bellows said, “Forgive me — a week ago I was on vacation.”