Three towns west of Portland have become a cash-fueled partisan battleground thanks to unprecedented spending on campaign advertising focused on protecting Democratic control of the Legislature and promoting party ideals at the state level.

In Senate District 30, which covers all of Gorham, most of Scarborough and most of Buxton, one-term incumbent Jim Boyle, D-Gorham, is being challenged in the Nov. 4 election by two-term Rep. Amy Volk, R-Scarborough. The largely rural district is one of seven Senate seats that are considered up for grabs.

The race has attracted more than $192,000 in campaign contributions so far, with the bulk of it – $164,598 – being spent on Boyle’s behalf, according to campaign finance reports filed with the state. The Maine Democratic State Committee leads the pack, spending $108,630 to back Boyle, including $52,340 on ads opposing Volk.

Political observers say the heightened spending, which grows almost daily, reflects Democrats’ concerns about retaining their Senate majority, as well as a national trend toward increased spending on state races in the wake of recent Supreme Court decisions loosening campaign finance regulations.

“Volk is a strong conservative who tends to elicit strong feelings on both sides,” said Jim Melcher, a political science professor at the University of Maine-Farmington. “Clearly some Democrats seem extra motivated to make sure she doesn’t move up to the state Senate.”

The spike in campaign spending in Maine is bolstered by the Supreme Court’s 2010 decision in the Citizens United case, which uncapped campaign expenditures, and a 2014 decision that eradicated biennial aggregate spending limits.

“That’s had a national effect, including here in Maine,” said Ron Schmidt, a political science professor at the University of Southern Maine.

Moreover, because of the current partisan gridlock in Congress, Schmidt said, “people are finding it difficult to get anything done at the national level,” especially on issues related to business, economic development, women’s health, voter access and the environment.

Spending by interest groups is growing as they try to push for greater access to lawmakers at the state level.

“You can spend more now in state races, where you get a bigger bang for your buck,” Schmidt said. “Mainers are going to have to get used to state politics looking more like national politics.”

Boyle’s $164,598 in contributions includes money from Planned Parenthood and from liberal or progressive political action committees, such as Citizens Who Support Maine’s Public Schools, Every Voice Maine and the Committee to Rebuild Maine’s Middle Class, plus some labor and environmental groups, according to reports filed with the Maine Commission on Governmental Ethics and Election Practices.

Volk’s $27,996 total consists of $6,439 from the Maine Republican Party, $19,786 from the Capital Leadership PAC and $1,771 from the Maine Truck PAC.

S. Donald Sussman, majority share owner of MaineToday Media, which publishes the Portland Press Herald/Maine Sunday Telegram, Kennebec Journal and Morning Sentinel, is a substantial donor to several political action committees supporting Boyle and other Democratic candidates.

Spending by outside groups is certain to exceed what the candidates raise and spend on their own. Boyle is a publicly funded Clean Elections candidate, which means his campaign can spend about $22,000 on the general election. Volk is a traditionally financed candidate and her campaign had about $25,000 in cash available as of Sept. 23, the end of the last filing period, according to records posted by the ethics and elections commission.

Leaders of both parties acknowledge significant interest in the outcome of the Senate District 30 race. Rachel Irwin, spokeswoman for the Maine Democratic Party, called it a “top priority.” David Sorensen, spokesman for the Maine Republican Party, said it’s “hugely important.”

Boyle, 56, operates Boyle Associates, an environmental consulting firm with seven employees. He said he would continue to work for business and job growth, environmental protection and clean, renewable energy. He also supports raising the minimum wage, expanding Medicaid, and protecting women’s reproductive rights and health care options. He has fought against charter schools and voucher programs as a drain on public school funding.

“I’m concerned about syphoning tax dollars away from brick-and-mortar schools,” Boyle said.

He noted his efforts as Senate chairman of the Environment and Natural Resources Committee and a member of the Agriculture, Conservation and Forestry Committee, including his sponsorship of bipartisan legislation that streamlined the permitting process for timber harvesting.

Volk, 45, operates Personally Yours, a home-based, custom-printed products service. Volk said she would continue to promote economic growth and jobs as she did as ranking minority member of the Labor, Commerce, Research and Economic Development Committee. She describes herself as a “moderate pro-life” candidate and said she opposes raising the minimum wage or expanding Medicaid as currently allowed and funded by the federal government.

Volk pointed to her sponsorship of legislation that helps victims of human trafficking as an example of her ability to win bipartisan support in a divided Legislature. She said she supports continued welfare and education reform, such as the recent formation of Maine Connections Academy, the online charter school that she helped to start as its board chair.

“I hear a lot about welfare reform,” Volk said. “The best form of assistance people can have is a good job.”