PORTLAND, Maine — The battle over who will represent Maine in the largest congressional district east of the Mississippi River is the most expensive political race in state history, leading to more television campaign ads than any other state and underscoring millions of dollars of so-called "dark money" pouring into the race.

That boils down to a rate of 26 commercials per hour, or about one every two minutes, according to the Wesleyan Media Project.

But whether those never-ending ads fueling the Democrat and Republican duking it out in Maine's 2nd Congressional District will sway voters is unclear with a few days to go before the state's Tuesday election.

"There are a ton of ads. It's pretty shocking how many ads there are," said John Hafford, a business owner in Medway. "One of the things I'm most alarmed with is how negative it's become. It's getting pretty rough out there."

The U.S. House race in the 2nd District, which covers most of the state and is overwhelmingly rural, has already broken records to become the most expensive in the state's history, with over $12 million in spending by outside groups so far.

That includes $2.3 million spent by liberal Patriot Majority USA, a nonprofit that doesn't have to disclose who funded its ads against Republican U.S. Rep. Bruce Poliquin. The congressman has tried to use misgivings about such spending to his advantage and argues that Democrats who have long railed about big money in politics are playing the same games.

"There's millions and millions of dollars pouring into this race from Nancy Pelosi, the extreme radical from San Francisco, or Maxine Waters. All this dark money," Poliquin said, in a recent campaign ad.

His challenger, Democratic state Rep. Jared Golden, who has decried dark money and distanced himself from Pelosi, recently vowed to require such groups to disclose their donors. The Congressional Leadership Fund, a super PAC linked to House Speaker Paul Ryan and funded partly by untraceable money, has spent $3 million to oppose Golden.

"A huge amount of money is going into that race. That tells you how close the race is, how important the race is, not just in Maine but nationally," said Mark Brewer, a political scientist at the University of Maine.

Meanwhile, at the state level, Democrats boosted by hard-to-trace money still have the spending advantage over Republicans with a few days to go before Election Day. National liberal groups like the Democratic Governors Association and the Democratic Legislative Campaign Committee have contributed heavily in Maine, partly in hopes of gain influence in redistricting following the 2020 census in Maine.

Democrats — who currently boast just 13 governors — also hope to win the governor's mansion and the state Senate, which Republicans currently control 18-17.

State campaign finance records show $9.6 million has been spent to boost Democratic candidates for state office, compared with $3.6 million spent helping Republicans.

At least $1.6 million in contributions to Maine races this year comes directly from groups that don't have to disclose their donors, including the League of Conservation Voters and Planned Parenthood's advocacy arm.

Democrats have outspent Republicans in Maine in recent years, and that hasn't always meant victory. While polling suggests frustration among some Mainers toward President Trump and outgoing GOP Gov. Paul LePage, the increasingly polarized state's vast 2nd Congressional District gave a historic single electoral vote to Trump in 2016.

In 2014, outside spending totaled $14.6 million in Maine state-level races. That year, $4.7 million was spent boosting Republican candidates, compared with $9.9 million on Democrats.