Campaigns and outside groups spent more money per voter in Maine than in all but one U.S. Senate race nationwide as the state became a front line in the battle for control of the Senate.

An analysis of spending reports shows that the $185 million spent by Democrat Sara Gideon, Republican Sen. Susan Collins and dozens of outside groups equated to $175 for every registered voter leading up to Collins’ re-election on Tuesday. That was second only to Montana’s Senate race, where campaigns and groups shelled out $232 for every registered voter.

To put that $175 into context, roughly $9 was spent per registered voter during Collins’ last re-election campaign in 2014.

Looking at election results, Gideon’s losing campaign ranked second in the nation, with at least $143 spent for every vote cast in her favor, based on unofficial results. Collins, who surprised many in Maine and Washington, D.C., with the margin of her victory, spent just shy of $57 for every vote she earned.

All of those figures are likely much higher, however, because they do not include any splurge by the candidates during the final three weeks of the race.

All told, the two campaigns, along with an army of political action committees, super PACs and other groups, have reported spending more than $185 million on the race and likely blew past the $200 million mark by the time votes were counted. In contrast, Maine’s previously most expensive campaign, the 2018 race for the 2nd Congressional District, saw roughly $24 million in spending.

“This is unprecedented levels of spending in Maine,” said Anthony Corrado, professor of government at Colby College who studies campaign finance issues at the national level. “We basically saw in 15 months the amount of money we had spent in every Senate and House race in Maine in two decades.”

The two independents in Maine’s Senate race, Lisa Savage and Max Linn, reported spending roughly $700,000 total.

Despite the record spending and consistent polling showing Gideon in the lead, Collins secured a fifth term in the Senate by a comfortable margin of 51 percent to 42 percent, according to unofficial election results. While Collins’ 72,000-vote advantage over Gideon was considerably smaller than her margins of victory in every previous re-election campaign, the incumbent was able to avoid a ranked-choice voting tabulation by winning a majority on the first count.

Collins was able to hold onto her seat despite being outspent by Gideon 2-to-1 as of mid-October – a dynamic that played out multiple times across the country this election as Democrats spent big but failed to oust Republican incumbents. While the breakdown of Senate seats is still unknown because of ongoing vote counting and planned runoffs, Gideon’s loss complicated Democrats’ path to a majority in the chamber.

Currently Maine’s House speaker, Gideon shattered every previous record in Maine in terms of both contributions and expenditures, thanks in large part to a flood of out-of-state money enabled by Democrats’ national fundraising machine. As of Oct. 14, the last date for which full campaign finance reports are available, the Freeport Democrat had raised $69.5 million and spent just shy of $49 million, with $20.7 million still sitting in her campaign coffers.

Looking at her “return on investment” on Election Day, Gideon spent nearly $143 for each of the 342,652 votes she received, based on the latest vote tallies.

Collins, by comparison, spent $23.6 million through Oct. 14 and had received 414,705 votes as of Friday’s counts — or roughly $57 for every vote. That was the eighth-highest amount among 2020 Senate candidates who had spent the most money, while Gideon’s $143-per-vote ratio ranked her second after Montana Gov. Steve Bullock, a Democrat who also lost despite outspending his Republican opponent.

But for every dollar spent by the Gideon or Collins campaign, outside groups spent a dollar more – with much of that of money financing a nonstop stream of attacks on television, radio, the internet and in the mail.

Sen. Susan Collins speaks to supporters near midnight Tuesday outside of the Hilton Garden Inn in Bangor. Brianna Soukup/Staff Photographer

Outside groups such as PACs, super PACs and nonprofits spent between $100 million and $110 million to either prop up or knock down the two frontrunners in Maine’s Senate race. The combination of candidates’ expenditures and outside spending – also known as “independent expenditures” because they are not supposed to be made in coordination with the candidates – is what gets Maine to at least $175 per registered voter.

The Center for Responsive Politics, a nonpartisan campaign finance watchdog group, lists more than two dozen groups spending anywhere from a few thousand dollars to tens of millions of dollars to influence Maine voters. The flood of outside money was almost equally divided between the candidates, with $61 million spent to either support Gideon or oppose Collins, and $50 million spent to support Collins or oppose Gideon.

At the top of the heap was the Senate Majority PAC, a group affiliated with Democratic Senate Minority Leader Chuck Schumer of New York, which spent $27.9 million to help Gideon and hurt Collins.

Not to be outdone, two of the Republicans Party’s biggest campaign operations – the National Republican Senatorial Committee and the Senate Leadership Fund – spent a combined $29.6 million to support Collins or hurt Gideon. Rounding out the Top 5 outside groups was 1820 PAC ($10.4 million), an organization created solely to defend Collins’ seat and bankrolled by a handful of wealthy individuals, and the Democratic Senatorial Campaign Committee ($4.7 million).

The Campaign Finance Institute, another nonpartisan group that analyzes political spending, has tracked roughly $1.1 billion in “independent expenditures” this year in U.S. Senate races alone. While races in Michigan, Iowa and North Carolina saw more last-minute outside spending, groups spent $4.9 million in the final week alone of Maine’s Senate contest.

Colby College’s Corrado, who serves on the board of trustees of the Campaign Finance Institute, said Maine’s Senate race will likely be among the Top 5 in total independent expenditures this year, despite the state having a pool of only about 1 million voters.

Democratic candidate for U.S. Senate, Maine House speaker Sara Gideon, speaks on Wednesday in Portland, where she conceded Tuesday’s election to incumbent Republican Sen. Susan Collins. Sara Gideon for Maine via Associated Press

“What we are seeing in Maine generally follows the pattern in the handful of other competitive races: enormous amounts of money spent by the candidates and unheard-of amounts of money from out-of-state to try to influence voters largely in the form of television advertising and campaign mail,” Corrado said.

But was it effective? Corrado was skeptical, particularly regarding the flood of last-minute spending in a race where polls suggest that most voters had made up their minds weeks before Election Day. Corrado said he believes Collins’ victory resulted more from successful messaging than the deluge of late-spending at a time when Mainers were being weary of the political bombardment on TV, over the radio, on their digital screens and in their mailboxes.

“What really changed the complexion of the race in the end was Susan Collins being able to focus the race on local issues and what she had done for the state of Maine,” he said.

During the campaign, both Collins and Gideon decried the level of spending by out-of-state organizations, often accusing the other of relying on so-called “dark money” groups to do the dirty work of the campaign.

Yet both candidates actively courted donors from outside of Maine in equal proportions. According to analysis by the Center for Responsive Politics, 92 percent of individual contributions to Collins and 93 percent received by Gideon came from outside of Maine.

No surprise to Mainers, all of that campaign cash and outside spending fueled an intensely negative campaign — one of the most negative in the country, in fact, in terms of advertising content.

Between Oct. 12 and 25 alone, Maine television networks aired 16,550 ads at a cost of $16.3 million to the campaigns and outside groups. The latter accounted for a higher percentage (49 percent) of television ads during that period in Maine than in any other state, according to an analysis by Wesleyan Media Project, a collaborative of researchers at several universities.

While the nation as a whole saw fewer attack ads in Senate races in 2020 than in previous years, Maine was one of the notable exceptions.

Nearly 60 percent of the television ads aired on Maine stations between Oct. 12 and 25 were attack ads compared to an average about 42 percent nationally, the Wesleyan Media Project found.