BILLINGS — Rep. Ryan Zinke, R-Mont., on Wednesday became the most prominent Montana Republican to endorse Donald Trump, one day before the presumptive nominee for the Republican presidential nomination arrives to rally supporters in the Treasure State.

Amid speculation about who Trump will enlist as part of his administration, Zinke, a former U.S. Navy SEAL commander, has said he would serve under Trump if called upon — perhaps as the New York businessman’s vice presidential pick or as Secretary of Defense.

“I know my name has been thrown around, and I would be honored to the duty in whatever capacity that is,” Zinke said in interview published on Wednesday by the conservative website Breitbart.com.

“I want to be a part of the team that’s making America great again in whatever capacity I can serve,” Zinke said.

The website said the interview was conducted Tuesday evening.

The congressman from Whitefish will introduce Trump at today’s rally at MetraPark Arena in Billings.

Superintendent of Public Instruction and Democratic U.S. House candidate Denise Juneau said Zinke should focus on representing Montana.

“Congressman Zinke seems to be more focused on helping special interests and boosting his own image, and not really focused on taking care of Montana,” she said.

“Ambition’s fine,” she said, “as long as you’re ambitious about doing your job that you’re elected to do.”

With his announcement Wednesday, Zinke becomes one of only a dozen members of Congress who have publicly endorsed Trump.

Other high-profile Montana Republicans, including Republican gubernatorial candidate Greg Gianforte, have said they would support their party’s eventual nominee, but have withheld outright endorsements for Trump thus far.

That didn’t stop Montana Democratic Party Chairman Jim Larson from linking Trump’s economic policies to those of Gianforte, a Bozeman businessman.

Tax plans offered by Gianforte and Trump offer similar “massive tax handouts to millionaires,” Larson said, adding that both plans risk upsetting the economy.

In a statement earlier this month, Sen. Steve Daines said his focus was on defeating Democratic hopeful Hillary Clinton. “Donald Trump is not my first choice or even my second choice for president,” he said.

But in an email, a spokeswoman for the senator said there would be an announcement made at the Trump rally, but she did not elaborate.

During an appearance Wednesday morning on Fox News, Zinke said it was time for him to make an endorsement. He followed that with a blast of press releases and postings on social media.

“As Montana’s Congressman, I know we need a new kind of President who knows the difference between the Potomac River and the Yellowstone River,” Zinke said in a statement.

Zinke he says he doesn’t agree with Trump on everything, but believes the New York businessman would be stronger on national defense than Clinton.

While Trump is the presumptive nominee, his name won’t be alone on the Republican presidential ballot in Montana’s June 7 primary. Texas Sen. Ted Cruz and Ohio Gov. John Kasich, along with Florida Sen. Marco Rubio and former Florida Gov. Jeb Bush will also be on the ballot.