This story will be updated.
Update 12:35 p.m.: Maine Secretary of State Shenna Bellows says voter turnout is high across the state, and could reach record levels for a midterm election.
Many voting locations reported lines out the door after opening as early as 6 a.m.
Bellows says it's possible that the U.S. Senate race will go to ranked choice voting. If it does, she says there may not be a final result until Wednesday or Thursday.
"It's better to get it right than go too fast and get it wrong. So we want to make sure that the will of the voters today is upheld in the count, and so that every voter has that comfort of knowing that their vote was counted accurately," she says.
Maine is one of only two states in the country, along with Alaska, where voters can rank candidates by preference. If a candidate breaks 50% of the vote, they win the election. If none do, the candidate with the fewest first-choice votes is eliminated, and votes are re-tabulated.
— Molly Enking, Maine Public
Update 12:28 p.m.: The U.S. Department of Justice has sent federal election monitors to three Maine cities. It's the first time that monitors have been dispatched to all 50 states. The DOJ says their mission is to ensure "compliance with federal voting laws."
Maine Secretary of State Shenna Bellows' office has promised to "watch the watchers."
"There was a lot of concern about DOJ monitors in South Portland, Portland, and Lewiston. They're doing exactly what they should be, sitting with other poll watchers from the main Republican and Democratic parties, as well as nonpartisan poll watchers and congressional observers, there in plain clothes taking notes," she says.
Bellows and her staff have been visiting polling locations throughout the state today. She says there have so far not been any reported disruptions or incidents.
— Molly Enking, Maine Public
Update 6:56 a.m.: Maine voters will head to the polls today to cast ballots in two races that could help determine control of Congress and to choose a new governor following the most tumultuous campaign season in recent state history.
Turnout is expected to be high for a midterm election even for Maine, which consistently has among the highest rates of voter participation in the country.
Maine will, once again, be in the national spotlight tonight because the state's U.S. Senate seat is one of a small number that could dictate which party can claim a majority next year. Several recent surveys show Democrat Troy Jackson maintaining or even enlarging his lead over Republican Sen. Susan Collins. But Collins defied the pollsters six years ago.
In the race for governor, Democrat Hannah Pingree has consistently led her two rivals, Republican Bobby Charles and independent Rick Bennett, in most polling. And whoever wins will have to work with a new Legislature as voters will fill all 186 House and Senate seats this year.
One of Maine's two U.S. House races has also drawn attention from the national parties and their allies.
Voters in Maine's 2nd Congressional will also choose whether former Republican Gov. Paul LePage or Democrat Matt Dunlap will fill the seat being vacated by Democratic U.S. Rep. Jared Golden after eight years.
In the 1st Congressional District, longtime incumbent Democratic U.S. Rep. Chellie Pingree is widely considered a safe bet for reelection over her Republican challenger, Ron Russell.
Most voting locations are open from 8 a.m. to 8 p.m., although some towns open earlier. But more than 300,000 voters — nearly a third of all registered voters — had already cast their ballots as of Monday evening, according to data from Maine's Secretary of State's office.
Affordability concerns have been top of mind for many voters in Maine and across the country this election. Many Democrats are also viewing the elections as a referendum on President Donald Trump as the war in Iran, tariffs and other factors drive up consumer costs.
Maine's tumultuous U.S. Senate race has largely overshadowed the other elections on the ballot for much of the past year thanks, in no small part, to the amount of outside political money flowing into the state. Jackson was also forced to quickly ramp up a campaign after the previous Democratic nominee, Graham Platner, withdrew from the race over the summer amid a scandal.
According to the tracking firm Ad Impact, Democratic and Republican groups groups spent more than $80 million on ads in Maine last month alone, with much of that money pay for attack ads against Jackson and Collins.
Only four other states — Ohio, Texas, Iowa and Michigan — saw more ad spending on Senate races last month, and all of those have much larger populations than Maine. A recent analysis by USA Today found that groups have spent more money per capita in Maine than on any other Senate race.
— Kevin Miller, Maine Public