Senate candidate Graham Platner will back out of all upcoming Democratic primary debates to focus on his campaign to unseat incumbent U.S. Sen. Susan Collins in November, his campaign confirmed Thursday afternoon.

Platner, an oyster farmer and military veteran, had been set to debate Gov. Janet Mills and David Costello, who has held a variety of positions in federal and state government, until Mills abruptly ended her campaign Thursday. The three had planned to appear in several debates in May, including one on May 7 hosted by NEWS CENTER Maine and Maine Public in partnership with the Portland Press Herald.

With Platner out of the debates and Mills out of the race entirely, it wasn’t immediately clear Thursday whether any of the debates would go forward as planned. Costello had been expected to attend at least three of the debates, though his low poll numbers meant that he failed to qualify for a May 18 forum hosted by WGME and the Bangor Daily News.

Maine’s Senate race has drawn attention from across the country, as Democrats have identified Collins as one of the Republican Party’s most vulnerable members.

Collins carries endorsements from heavy-hitting Republicans like Senate Majority Leader John Thune of South Dakota and Tim Scott of South Carolina, chair of the National Republican Senatorial Committee.

President Donald Trump has gone back and forth in his characterization of Collins. In a March television appearance, he included her among a group of Republicans he was “not at all fans of,” before calling her a “good person” and saying that he hopes she wins.

Collins has also received widespread support from Republicans within Maine. Some of that enthusiasm was on display over the weekend at the state GOP’s convention — where the senator tossed hats into a high-energy crowd.

Platner, for his part, has secured a long list of endorsements from national progressive groups like College Democrats of America and David Hogg’s Leaders We Deserve, as well as local organizations like the Maine People’s Alliance and the Maine State Nurses Association. He has campaigned alongside Troy Jackson, the former Maine Senate president who is running for governor.

Platner also announced a slew of new Maine endorsements Thursday, just hours after Mills withdrew from the race.

Nationally, he’s also been backed by Democratic Sen. Elizabeth Warren of Massachusetts and independent Sen. Bernie Sanders of Vermont, who reiterated his support in a Thursday post on X.