U.S. Senate candidate Graham Platner appeared in Portland on Tuesday alongside three prominent Maine Democrats who are seeking the party’s nomination for governor.

But Platner, a political newcomer who is generating national buzz, including a recent appearance on the cover of Time magazine, said he was not making a formal endorsement in the race.

“I just competed in a primary where the D.C. establishment tried to play kingmaker,” Platner said at the media event on the Western Promenade. “And so I’m not issuing any endorsements. But I was extraordinarily proud to cast my vote for governor for the three candidates here today.”

Platner, appearing alongside former Maine House Speaker Hannah Pingree, former Maine Senate President Troy Jackson and Secretary of State Shenna Bellows, was referring to his primary against Gov. Janet Mills. She was the preferred candidate of Senate Minority Leader Chuck Schumer until she suspended her campaign late last month.

Mills will still appear on the ballot, as will David Costello, of Brunswick. Bangor labor activist Andrea LaFlamme is running as a write-in.

The unusual news conference comes two weeks before the June 9 primary. It reflects how the candidates are positioning themselves in a ranked-choice election.

Voters can rank the candidates in order of preference. If no one wins a majority in the first round, an instant runoff occurs. Platner has said he will rank Jackson first, Bellows second and Pingree third.

A voter’s ballot stays with their first choice until that candidate is eliminated. Instant runoffs continue until a candidate gets a majority.

Little independent polling has been conducted in the race. Last week, the Portland-based Pan Atlantic Research released a survey showing none of the five Democratic candidates getting a majority in the first round.

The poll showed that 39% of respondents ranked former Maine Center for Disease Control and Prevention Director Nirav Shah as their first or second-place choice, followed by 33% for entrepreneur Angus King III, 32% for Pingree, 31% for Bellows and 18% for Jackson. Sixteen percent were undecided.

Jackson, Bellows and Pingree previously appeared together last month when they were all endorsed by the Sierra Club. And last week, they issued a news release about forming a ranked-choice alliance.

On Tuesday, the trio heaped praise on each other, while urging people to mark their names first on the ballot. They also praised Platner, who wasn’t around to hear the compliments because he left the event immediately after his short remarks.

Shah was asked about the alliance at a press event he held Tuesday about ending childhood hunger. He said that he has “nothing but respect” for his opponents and their records.

“That said, my campaign is about something different,” Shah said in a video shared by his campaign. “What I think we need is a fresh look at long-standing challenges in Maine, and that is what my campaign offers. That is one reason my campaign is leading in the polls.”

King dismissed the alliance, saying he’s running because “our politics weren’t meeting the moment” and that he’s focused on finding positive solutions.

“Having insiders cut a deal with each other doesn’t change my view, and I’m going to continue talking with voters about how we build a better Maine,” King said in a written statement. “Mainers don’t need to be told how to vote — they need real solutions and that’s what I’ll deliver.”

Both Platner and Jackson have been endorsed by Sen. Bernie Sanders, I-Vt., who held rallies in Orono and Portland with the candidates over the weekend.

Platner previously said he marked Jackson first on his ballot because of his pro-labor positions.

On Tuesday, Platner said he supported all three, not only for their policy positions on issues such as universal healthcare and childcare, but because of the groups supporting those candidates.

He noted that Jackson is backed by unions; Bellows is backed by the Maine People’s Alliance; and Pingree by environmental groups.

“I think those endorsements reflect our shared values, our shared politics and our shared vision for rebuilding the power of working Mainers,” Platner said. “I voted not just on policy positions, but for the movement I hope to see in Maine.”