Jon Treacy, an Oxford County Democrat and retired Air Force general, confirmed Tuesday that he will run a primary campaign for his party’s nomination to unseat U.S. Sen. Susan Collins in 2020.

Treacy, a 34-year veteran of the Air Force who retired as a two-star major general, filed nomination papers for the seat in July. He joins three other Democratic hopefuls, including Speaker of the Maine House Sara Gideon, long-time progressive activist and lobbyist Betsy Sweet and Bre Kidman, a Saco attorney.

“I absolutely believe our nation has been led down the wrong path into serious trouble — and consequently the state of Maine suffers as well,” Treacy said in a prepared statement issued by his campaign. “I spent my career serving this country but is our government serving us now?”

Gideon is leading the Democratic field in building a campaign war chest, so far raising just over $1 million, with an estimated $919,000 cash on hand at the end of the last federal filing in June.

Collins was sitting on five times that amount at the end of the last filing period. Collins’ seat is a top target for Democrats in a race that is expected to draw unprecedented amounts of outside spending to the state.

The Democratic effort to unseat Collins will get a boost from presidential candidate Elizabeth Warren, who told supporters in an email Tuesday that her campaign plans to invest in Maine and other states with competitive Senate and House races, as well as selected state legislatures.

Collins, who has attended multiple fundraising events, has yet to officially announce her reelection campaign.

The next filing campaign finance deadline for candidates is Oct. 15.

Treacy is the latest military veteran to seek a Democratic nomination for a statewide race. In 2018, Adam Cote, Sanford attorney and 20-year combat veteran and officer with the Maine National Guard, made an unsuccessful bid to become the party’s nominee for governor but lost to Janet Mills.  Also in 2018 Jared Golden, a Marine Corps veteran from Lewiston with combat service in Iraq and Afghanistan was elected to the U.S. House, unseating 2nd District Republican Bruce Poliquin and leaving Collins as the only Republican from New England in Congress.

Treacy also started his career in the Marine Corps before transitioning to the Air National Guard, where he remained on flying duty for 27 years and was the commander of the Massachusetts-based 101st Fighter Squadron, the first unit launched in the response to the terrorist attacks of Sept. 11, 2001.

“I believe Maine needs the kind of Senator who will fight for what is best for Maine and our nation, and not posture, equivocate, or offer platitudes in order to further their own political objectives,” said Treacy.