AUGUSTA (AP) — Independent U.S. Sen. Angus King of Maine is preparing to face a challenge from two lesser-known candidates in the November election.

Republican State Sen. Eric Brakey was unchallenged in his primary election Tuesday after an opponent, Max Linn, was disqualified after election officials determined his nomination petition contained fraudulent signatures. Portland Democrat Zak Ringelstein was also unopposed.

King was first elected in 2012 after Republican Sen. Olympia Snowe abruptly abandoned her re-election bid, citing corrosive partisanship in Washington.

King said in announcing his formal re-election bid a few weeks ago that he wants to continue his effort to serve as a bridge between the polarized parties. He said there are "tender shoots of bipartisan cooperation" that need to be encouraged.