Democratic candidate for governor Troy Jackson is calling on his opponents in the primary to join him in rejecting spending by wealthy outside groups on the election.

Jackson has signed the “People’s Pledge,” a deal first developed by Democratic U.S. Sen. Elizabeth Warren of Massachusetts and her Republican opponent, Scott Brown, in 2012. The two candidates called on outside groups to stop spending on their behalf.

“Folks are tired of the influx of dark money into our politics from both parties,” Jackson said in a written statement. “We need to band together and reject outside dark money in our primaries.”

The pledge calls for candidates in the Democratic primary to oppose “independent expenditures by wealthy, corporate and dark money groups” and calls on campaign supporters to either volunteer their time or donate directly to candidates.

Since the 2010 Supreme Court decision in the case Citizens United v. Federal Election Commission, interest groups around the country have been allowed to spend unlimited sums in support of their preferred candidates.

However, Jackson, a former Maine Senate president from Allagash, says he’s not willing to unilaterally disarm in the spending race. If his rivals don’t sign the pledge, he won’t abide by it, either.

Jackson has seen the effects of outside spending firsthand. His 2022 Maine Senate race against Republican Sue Bernard drew close to $1 million in such spending — the majority of which benefitted him.

Six Democrats are running for the party’s nomination on June 9. Several of Jackson’s primary opponents said Tuesday they support campaign finance reform and agree that there needs to be less outside spending, but did not say they would also take the pledge.

For example, a spokesperson for former Maine Speaker of the House Hannah Pingree said in a statement Tuesday that Pingree believes “elections should be decided by Maine voters, not by big outside money or special interests,” but called the pledge “unenforceable.”

No outside spending has been officially logged yet in this year’s governor’s race, though the conservative Restoration of America PAC has reportedly spent hundreds of thousands of dollars on television ads in support of Republican Garrett Mason.

State campaign finance reports covering the first quarter of the year are not due until April 10.

In the 2022 governor’s race, spending by independent groups far exceeded that of candidates.

More than $20 million was spent that year by outside groups, including state parties and political action committees. Just over $8.3 million was spent by the three candidates — Democratic incumbent Janet Mills, former Republican Gov. Paul LePage and independent Sam Hunkler. Neither Mills nor LePage faced primary opponents in 2022.