Democrat Sara Gideon raised $8 million for her campaign for Maine’s U.S. Senate seat between April and late June, more than doubling the fundraising haul of incumbent Republican Sen. Susan Collins during the same period.

Maine’s 2020 Senate competition is already the most expensive campaign in state history and is likely to continue drawing national attention – and money – through November. Collins and Gideon, who is the frontrunner in a three-person Democratic primary field, have raised more than $39 million to date, with tens of millions more flowing into and out of political groups supporting the two campaigns.

Republican Sen. Susan Collins, left, reported $16.3 million in contributions as of June 24, while Democrat Sara Gideon reported $23 million. Both campaigns have relied heavily on out-of-state donors.

Gideon, who is speaker of the Maine House of Representatives, raised $8.1 million from April 1 to June 24, according to pre-primary financial reports filed Thursday with the Federal Election Commission. Collins, meanwhile, reported raising just over $3 million during that time as she seeks a fifth term in Congress.

Collins faces no opposition in the July 14 Republican primary. Three Democrats, meanwhile, will vie for their party’s nomination during the ranked-choice primary: Gideon, lobbyist and advocate Betsy Sweet of Hallowell, and attorney Bre Kidman of Saco. Sweet reported raising $228,585 in her pre-primary filing while Kidman reported raising $2,563.

Gideon continues to outpace Collins in fundraising – reporting $23 million in contributions as of June 24 versus $16.3 million for Collins – but has also spent more than her would-be opponent. The result is that the two potential contenders are headed into the summer months with nearly the same amount in the bank: $5.5 million for Gideon and $5 million for Collins.

Both the Collins and Gideon campaigns have relied heavily on out-of-state donors, although the Gideon campaign said nearly 13,500 Mainers have donated to the candidate so far.

And others have pointed to the huge sums flowing into and out of the two high-financed campaigns as indicative of the problems of money in politics today.

“To be clear: that amount of money COULD have been $500K in relief to each of Maine’s 16 counties to help deal with pandemic related shortfalls while STILL spending hundreds of thousands of dollars more than anyone else in the primary election,” Kidman said via tweet in response to Gideon campaign’s claim of raising $9 million for the full fiscal quarter.

The Collins and Gideon campaigns released statements reflecting their lines of attack on the other, with the Democrat portraying the incumbent as unresponsive to Mainers’ interests and the Collins camp questioning the Maine House speaker’s leadership during the COVID-19 pandemic.

“Mainers are ready for a new U.S. Senator, and since we launched our campaign last year, I’ve listened to and heard from thousands of Mainers across the state about the challenges they face and the kind of representation they need in Washington,” Gideon said in a statement. “It’s clear that Senator Collins has changed, and Mainers deserve a senator who will fight for them to reduce the influence of big money and special interests in our politics, increase access to affordable health care, lower the cost of prescription drugs, and take bold action to fight climate change.”

Collins spokesman Kevin Kelley, meanwhile, pointed out that the senator co-authored the Paycheck Protection Program that has funneled more than $2 billion in coronavirus-related assistance to businesses in Maine.

“The Maine legislature didn’t meet one day during this entire quarter – not once in the midst of the worst health and economic crisis of our lifetime,” Kelley said in a statement. “It’s clear where Speaker Sara Gideon’s priorities are. Sara spent the past 108 days calling out-of-state billionaires, raising money for her Senate campaign, while Maine’s unemployment system cratered. Thousands of Maine people lost their jobs and they still can’t get help from the state.”

Maine’s U.S. Senate campaign is already the most expensive in state history and is widely expected to be among the most costly – and high-profile – Senate races in the country this year. Democrats are hoping to flip Maine’s seat as part of their push to recapture control of the Senate.

But Collins is a formidable campaigner with a high national profile because of her committee assignments in Washington – including on the Senate Intelligence Committee – and her reputation as a potential swing vote on many contentious, partisan issues.

Outside organizations have already spent more than $13 million on Maine’s Senate campaign, according to data compiled by the Center for Responsive Politics, which is a campaign finance watchdog group. Roughly half of that total has paid for ads and other materials opposing Collins. The two biggest outside spenders to date are the Democrats’ Senate Majority PAC and the National Republican Senatorial Committee.

Campaign finance filings for the fiscal quarter ending June 30 are not due to the FEC until July 15. But Gideon’s campaign reported that the the candidate raised more than $9 million for the full quarter ending June 30.