BANGOR, Maine — The Bangor-area state Senate matchup between Republican Sen. Nichi Farnham and Democrat Geoffrey Gratwick is attracting more spending from outside groups than any other state legislative race this election cycle.

The $326,000 spent by the state’s two political parties and a handful of political action committees has led to a barrage of mailings, TV ads and radio spots aimed at Bangor and Hermon residents as they decide how to vote on Nov. 6.

“We should have a sense of outrage that this election is being decided by outside money,” said Gratwick. “If I lose, it’s going to be not because of my message. It’s going to be because of untruths told by people from away.”

Farnham said she’s trying not to let the messages from outside groups get in the way of her own. “That is a disheartening aspect when there is an exchange of messages beyond the scope of my immediate campaign,” she said. “I’m still focusing on my plan of getting out to voters door-to-door in my running shoes.”

As of Wednesday, outside groups had spent the majority of the $326,000 on publicity opposing the candidates. Republican-allied groups had spent $149,000 opposing Gratwick and $18,000 supporting Farnham. Groups allied with Democrats had spent $105,000 opposing Farnham and $54,000 supporting Gratwick.

Outside spending has surpassed the $100,000 mark in four other state Senate races, according to the Maine Ethics Commission. Outside groups have spent $190,000 in Senate District 6, where Republican Ruth Summers of Scarborough — wife of Maine Secretary of State Charlie Summers, the Republican candidate for U.S. Senate — is facing Democrat Jim Boyle of Gorham. And in Senate District 17, outside groups have spent nearly $146,000 on the matchup between first-term Sen. Garrett Mason, R-Lisbon, and Democratic challenger Colleen Quint of Minot.

Races in Senate District 15, where Sen. Lois Snowe-Mello, R-Poland, is defending her seat from a challenge by Auburn Democrat John Cleveland, and Senate District 25, where Waterville Democrat Colleen Lachowicz is trying to unseat first-term Republican Sen. Tom Martin of Benton, have also crossed the $100,000 mark in outside spending.

Statewide, outside groups had spent $1.9 million on state legislative contests as of Monday morning, setting a new record with two weeks to go before the Nov. 6 election. That amount exceeded the $1.5 million total spent in 2010, which was more than double the $635,000 spent in 2008.

The spending is likely to only pick up between now and Election Day, as it typically does in the two weeks before an election, said Jonathan Wayne, executive director of the Maine Ethics Commission.

“Particularly in the districts that are viewed as more competitive, when voters see paid mailings and ads, the chances are pretty good they’re being paid for by groups other than the candidates’ campaign,” he said.

Under Maine election law, outside groups generally can’t coordinate their spending with candidates.

Both Gratwick and Farnham are receiving public funds for their campaigns under the Maine Clean Election Act, which means they’re limited to spending about $21,000 each on their own campaigns, a fraction of the amount outside groups have spent.

The outside spending started at the beginning of August when the Maine Democratic Party included Farnham in a TV ad campaign that labeled her and four other Republican incumbent senators “rubber stamps” for Gov. Paul LePage’s agenda.

Democrats have also sent out a series of pro-Gratwick and anti-Farnham mailings, and they recently launched a $70,000 pro-Gratwick TV ad campaign.

The state Republican Party got involved in the race in mid-September with pro-Farnham and anti-Gratwick mailings.

Aside from the parties, outside spending in the race has been dominated by two other groups: the Maine Senate Republican Majority PAC and the Committee to Rebuild Maine’s Middle Class.

The Senate Republican Majority PAC purchased $73,000 in anti-Gratwick TV ads at the start of October and purchased $55,000 more a week later, according to expenditure reports on file with the Maine Ethics Commission.

“Nichi’s been a terrific senator, and it’s obviously a tight race,” said Sen. Roger Katz, R-Augusta, one of the PAC’s officers. “Media buys are more expensive in Bangor than they are in some other areas.”

The Senate Republican Majority PAC’s largest donor is the Republican State Leadership Committee, a Washington, D.C.-based, business-backed group that spent $400,000 to boost Republicans in five state Senate races in 2010, including the Bangor Senate race. The committee later faced a $26,000 fine from the state ethics commission due to late and inaccurate expenditure reporting.

This election season, the Senate Republican Majority PAC’s first ad buy triggered an election complaint from the Democratic Party alleging that Farnham illegally funneled the Senate Republican Majority PAC’s money into her race because she was listed as a principal officer on the PAC’s registration documents. Ethics commission staff on Wednesday released their finding that Farnham wasn’t at fault in the situation, but that the PAC should have removed her name from its registration documents months ago.

That complaint, filed with the Maine Ethics Commission, has become a subject of anti-Farnham TV and radio ads run by the Committee to Rebuild Maine’s Middle Class, a political action committee that incorporated in July. The group has also run phone banks and sent volunteers to canvass voters on Gratwick’s behalf.

“What we’re seeing is a difference between candidates who are standing with hard-working Mainers and will stand up for their best interest and those who sold out hard-working Mainers to big business,” said Nicola Wells, a spokeswoman for the committee. “That’s an issue we see at play in that race, and that’s why we’re getting involved.”

The committee has received the bulk of its support from unions such as the National Education Association, the Maine Education Association and the American Federation of State, County and Municipal Employees, according to campaign finance filings. As of Tuesday, the group had spent $41,000 so far on the Farnham-Gratwick race.