AUGUSTA — Hoping to capitalize on voter frustration over growing polarization in politics, a group fueled partly by so-called “dark money” plans to spend $3 million this year to elect independents. But some free-spirited lawmakers are declining their help.

Unite America, formerly known as the Centrist Project, is endorsing and providing polling for independent gubernatorial and legislative candidates in Maine and across the country.

It’s time state legislatures and governor’s mansions reflect the increasing proportion of U.S. citizens identifying as independents, said the group’s spokesman, Nick Troiano.

Polls suggest about four in 10 U.S. adults identify as independent; in 2000, fewer than three in 10 did so.

“Independents are independents because they won’t want to be told what to do or what to think,” Troiano said.

But some independents are reluctant to accept the support because they distrust influence by any outside special interest group.

They’re also leery of dark money – contributions from groups such as nonprofits that don’t have to disclose their donors under federal law.

It’s tricky for independent lawmakers – who often aim to offer dissatisfied voters an alternative to the big-money, two-party system – to accept such help even from a group with similar aims.

“What ails American politics right now is dark money,” said University of Massachusetts Boston political science professor Maurice Cunningham. “You can’t cure that with dark money.”

The offer for help, nonetheless, can be enticing for independent lawmakers who face an uneven playing field for campaigning and, once elected, legislating.

Unite America has released endorsements of candidates including incumbent Alaska Gov. Bill Walker. It also offers funding for resources that parties typically provide, including staffers, help finding donors, voter data, publicity, research, polling and help organizing campaign volunteers.

“We are not a party,” Troiano said. “We are a support structure.”

In Maine, questions over who should fund such support, and how, have stoked tension among independent lawmakers who include former Democrats and Republicans.

Unite America discloses its donors to its political action committees, which can make independent expenditures on behalf of candidates. Video game company Riot Games co-founder Marc Merrill has contributed $285,000 since last December to Unite America’s political action committee, according to recent federal campaign finance reports.

But Unite America does not publicly disclose all of its spending for or its donations to its two nonprofit arms: Unite America Inc. and Unite America Institute. Those nonprofits fund efforts such as polling and voter outreach.

Unite America offered to fund resources like staffers for independent Maine lawmakers, some of whom had lost access to party-provided staffers.

One of the group’s nonprofits funded an intern for independent state Rep. Owen Casas, who conferred with the state’s ethics commission and the Legislature’s executive office and found that outside, private groups could fund legislative staffers.

“There’s nothing that prevents charitable organizations from hiring staff that helps folks do their job currently,” said Casas, who also disclosed that he received income for writing a report for a Unite America research project on independents.

But independent Rep. Denise Harlow fears private funding of staffers could close the door to future public funding for staffers for independents. Or, Harlow said, independents could inadvertently encourage special interests like lobbying firms to seek political favor by funding partisan staff positions at the State House.

Elsewhere, Unite America is working to elect enough independent lawmakers in Colorado, New Mexico, Alaska and Washington to deny political parties a majority. The group has also endorsed candidates in Kansas, Missouri and Maryland.

Troiano said the group is optimistic about its chances in states like Alaska, where a group of House Democrats, Republicans and independents are caucusing together in a year marked by compromise.

And in Vermont, a group of independent representatives has begun to meet regularly and demand access to the same information that party leaders receive, said Rep. Laura Sibilia, who’s endorsed by Unite America.

Maine Rep. Kent Ackley, meanwhile, rebuffed such “outside moneyed influences” and didn’t seek Unite America’s endorsement. Instead, Ackley runs as a publicly financed candidate.

“I’ve been a proponent of saying no to organized efforts to help independents nationally,” said Ackley, who is rated highly by environmental and liberal groups.