Voters and poll workers buzz about the Cross Insurance Center, Bangor's polling place, during the primary election on June 14, 2022. Credit: Sawyer Loftus / BDN

AUGUSTA, Maine — Maine has added roughly 60,000 new registered voters on net since the last gubernatorial election, a voting bloc large enough to sway the matchup between Gov. Janet Mills and former Gov. Paul LePage this fall.

Democrats have added nearly twice as many new voters than Republicans during that period. But the data released by the Maine secretary of state’s office from just before the June 14 primary show increasing geographic polarization of voters in Maine. It provides the clearest picture yet of the landscape ahead of the governor’s race this November.

A notable difference from just four years ago is the decline in a sharp number of voters not enrolled with a major party. Just 32 percent of active registered Maine voters are unenrolled, compared with roughly 37 percent a decade ago. That group of voters has been a key part of the political identity for decades in a state that has elected two independent governors.

It is not clear whether the decline in unenrolled voters will have significant electoral implications, as research has generally found that the vast majority of independents — 81 percent in one Pew Research study — already lean toward one party or the other. Previously unenrolled voters who registered with the party they already leaned toward are unlikely to sway an election.

But the decision of more voters to register with a major party reflects national polarization, said Mark Brewer, a political science professor at the University of Maine in Orono.

“Twenty years ago, Maine politics was very different than American politics as a whole,” he said. “I think that’s become less true over time, particularly over the last decade.”

The net increase in active voter registrations for both parties occurred mostly in the lead-up to the 2020 presidential election. The total number of active registered voters declined by roughly 20,000 since November 2020, the data show. Voters are removed from the rolls if they die or move or if they do not respond to address confirmation from the state and do not vote for consecutive general elections.

The data also show the number of voters registered as Greens has also ticked up, while the number of Libertarians has dropped substantially, although the latter was the automatic unenrollment of its members under a Maine law dissolving parties dropping below a certain enrollment threshold. It was ruled unconstitutional last fall.

The voter registration data also show diverging partisan trends in different parts of the state, with Republicans making gains in northern Maine and inland towns, while Democrats’ margins grow in liberal southern and coastal towns.

For example, the Portland suburbs of Falmouth, Yarmouth and Cape Elizabeth added a combined nearly 2,700 registered Democrats over the four-year period while losing nearly 400 registered Republicans.

Republicans made gains over Democrats in voter registration in more than 300 towns, the data show. They netted the most total voters — about 850 total — in Winslow, Rumford and Madawaska, while having even greater percentage gains in sparsely populated townships.

Most of the municipalities where Republicans have made the most gains lie in the swing 2nd Congressional District. In 2018, registered Republicans in the 2nd District outnumber Democrats by a bit more than 1,000, according to state data.

Even with the district growing slightly more favorable toward Democrats with the addition of several Democratic-leaning towns in Kennebec County during redistricting, Republicans’ voter registration advantage over Democrats now stands at roughly 4,700. That is still a close margin, but one that could make a difference in a close congressional race.

U.S. Rep. Jared Golden, a Democrat, faces challenges from former Rep. Bruce Poliquin, a Republican, and unenrolled candidate Tiffany Bond in the competitive district this fall. The election will use ranked-choice voting.