Gov. Janet Mills will not attend a primary candidate forum hosted by the Wabanaki Alliance on the Penobscot Nation reservation on April 16.

Graham Platner, the Sullivan oyster farmer and Iraq War veteran running an insurgent campaign, and lesser known candidate David Costello, of Brunswick — both Democrats running against Mills in the primary — plan to go.

The Mills campaign, which did not immediately respond to a request for comment Tuesday, told the Wabanaki Alliance Monday that the governor has a scheduling conflict that night.

Republican Sen. Susan Collins, the incumbent, was not invited to the forum.

Mills offered to meet with the alliance board of directors at another date and send a surrogate or a video message to the April event in her stead. The board is still considering those proposals, according to Maulian Bryant, the organization’s executive director.

Candidates send messages with where they choose where to spend their time, Bryant said.

Donna Loring, vice president of the alliance Board, a former Penobscot tribal representative in the legislature and one-time advisor to Mills on tribal affairs, echoed Bryant’s remarks in a written statement.

“I’m not interested in criticizing anyone personally, but these moments are important,” Loring said. “They are opportunities to listen, to engage, and to stand before the people and have an honest conversation. When that doesn’t happen, people notice.”

Although the alliance board has not decided whether it will make any endorsements before the June 9 primaries, Bryant said she was “encouraged that we do have candidates that will be coming to engage with us.”

The governor in her final year in office has made halting progress to mend her relationship with the Wabanaki Nations. Throughout her two terms, Mills has clashed with members on the state-tribal commission, repeatedly quashed or diluted legislation that introduce sweeping changes to recognize tribal sovereignty and skipped a 2023 state of the tribes address before the legislature (also citing a scheduling conflict).

However, she has also found common ground with tribal leaders on economic issues of late, including legislation to expand tax cuts for tribal members and businesses. In January, she allowed a bill to become law legalizing tribal operations of internet gaming in Maine. The bill seemingly challenged the governor’s sensibilities with respect to gambling, but was a key priority for tribal leaders.

The decision earned her ecstatic praise from tribal leaders, one of whom called her the “greatest ever Maine Governor champion for Wabanaki progress.”

As she makes her bid for the Senate, Mills is trailing Platner in most polls. Platner has come out as a no-holds-barred supporter of tribal sovereignty and stopped by a committee hearing on the latest legislation in February to say so.

Independent candidate Tim Rich has not responded to the alliance’s invitation.

Reuben M. Schafir is a Report for America corps member who writes about Indigenous communities for the Portland Press Herald.