BOZEMAN, Mont. (AP) — With control of the Senate potentially at stake, Donald Trump is visiting Montana on Friday hoping to remedy some unfinished business from 2018, when he campaigned repeatedly in Big Sky Country in a failed bid to oust incumbent Democratic Sen. Jon Tester.

Tester has tried to convince voters he's aligned with Trump on many issues, mirroring his successful strategy from six years ago. While that worked in a non-presidential election year, it faces a more critical test this fall with Tester's opponent, former Navy SEAL Tim Sheehy, trying to link the three-term incumbent to Democratic presidential candidate Kamala Harris.

Harris has benefitted nationally from a burst of enthusiasm among core Democratic constituencies, who coalesced quickly around her after President Joe Biden withdrew from the campaign last month. She's drawn big crowds in swing states, touring this week with Minnesota Gov. Tim Walz, her choice to be her vice presidential nominee.

Trump's only rally this week, meanwhile, will be in a state he won by 16 percentage points four years ago rather than a November battleground. Facing new pressure in the race from a candidate with surging enthusiasm, Trump on Thursday called questions about his lack of swing state stops "stupid."

"I don't have to go there because I'm leading those states," he said. "I'm going because I want to help senators and congressmen get elected."

He will add on fundraising stops in Wyoming and Colorado.

Trump could be decisive in Montana's Senate race

Friday's rally at Montana State University, which starts at 8 p.m. Mountain time, is expected to draw thousands of GOP supporters. Yet the former president's bigger impact could be simply having his name above Sheehy's on the ballot in November, said University of Montana political analyst Rob Saldin.

"There is a segment of the electorate that will turn out when Trump is on the ticket," Saldin said. And that could benefit Sheehy, a Trump supporter and newcomer to politics who made a fortune off an aerial firefighting business.

Republicans have been on a roll in Montana for more than a decade and now hold every statewide office except for Tester's.

Tester won each of his previous Senate contests by a narrow margin, casting himself as a plainspoken farmer who builds personal connections with people in Montana and is willing to break with his party on issues that matter to them. He's also become a prolific fundraiser.

The race has drawn national attention with Democrats clinging to a razor-thin majority in the Senate and defending far more seats than the GOP this year. Tester is considered among the most vulnerable Democratic incumbents.

For him to win, large numbers of Trump supporters would have to vote a split ticket and get behind the Democratic senator.

Trump's drive to oust Tester traces back to the lawmaker's role in 2018 as chairman of the Senate Committee on Veterans' Affairs. Tester revealed past misconduct by Trump's personal physician, Ronny Jackson, that sank Jackson's nomination to lead the Department of Veterans Affairs.

Then-President Trump took the matter personally and came to Montana four times to campaign for Republican Matt Rosendale, who was then the state auditor. Rosendale lost by 3 percentage points.

Tester has positioned himself apart from national Democrats

Ahead of Trump's latest visit, Tester has sought to insulate himself against charges that he's part of the Democratic establishment by rolling out the names of Republicans who support him, including former Montana Gov. Marc Racicot. His campaign highlighted more than 20 pieces of legislation, many dealing with veterans' issues, that Tester sponsored and Trump signed.

Tester also was the sole Democratic delegate from Montana to withhold a vote backing Harris as the party's presidential candidate in the wake of Biden's withdrawal. And when the Democratic National Convention takes place later this month in Chicago, Tester will be back in Montana "farming and meeting face to face with Montanans," campaign spokesperson Harry Childs said.

The last time Tester attended the Democratic National Convention was in 2008. That's also the last time a Democratic presidential candidate came anywhere near winning Montana, with President Barack Obama losing by just over 2 percentage points.

Friday's rally takes place in Gallatin County, which Tester has become increasingly reliant on over the course of his political career.

He lost the county in his first Senate race, in 2006, but his support has since grown. A substantial margin of victory in Gallatin in 2018 helped push him ahead of Rosendale.

Republican Don Seifert, a former Gallatin County commissioner, said he voted for Tester that year and plans to do so again this year.

Seifert backed Trump in 2016 and said he has continued to support other Republicans, including Montana Gov. Greg Gianforte and Sen. Steve Daines.

"Montanans tend to vote for the person over the party," Seifert said. "For the state of Montana, Jon is that one that can do what we need."

But Sheehy says Tester has lost touch with his home state and fallen into step with Democrats in Washington. The Republican alleged in a message this week to supporters that Tester was "responsible for the rise of Kamala Harris" because he served as chairman of the Democratic Senatorial Campaign Committee from 2015 to 2017, when she was elected to the Senate from California.

Tester has outraised Sheehy by more than three-to-one in campaign donations reported to the Federal Election Commission. However, outside groups supporting Sheehy have helped the Republican make up much of that gap, pouring tens of millions of dollars into the race as advertisements from the two sides saturate Montana's airwaves.