JUNEAU, Alaska (AP) — President Donald Trump on Tuesday endorsed Alaska U.S. Sen. Dan Sullivan’s re-election.

In a tweet, Trump said the Republican Sullivan is doing a great job for the state while also supporting Trump’s agenda.

Sullivan, a former state attorney general and natural resources commissioner, was elected to the Senate in 2014. In the Senate, he has been involved in military and resource development issues and efforts to address marine debris. He is a colonel in the U.S. Marine Corps Reserve.

Sullivan campaign manager Matt Shuckerow, in a statement, said Sullivan welcomes the endorsement and thanks Trump and his administration “for their ongoing work with the Congress to make Alaska a stronger, more prosperous and resilient state.”

Sullivan’s highest profile challenger so far is Al Gross, an independent who earned an early endorsement from the state Democratic party.

Gross left his practice as an orthopedic surgeon to focus on ways to change the health care system, according to a campaign video. He has made addressing what he sees as a broken health care system a major issue in his campaign.

Gross’ father, the late Avrum Gross, was an attorney general under former Gov. Jay Hammond.