BOZEMAN, Montana (AP) — Former President Donald Trump was scheduled to travel to Montana Friday night for a rally to oust the state’s Democratic senator from office, but his plane had to be diverted to an airport on the other side of the Rocky Mountains because of a mechanical problem, according to airport officials.

According to Jenny Mockel, administrative assistant at Billings Logan International Airport, Trump’s plane was en route to Bozeman, Montana, when it was diverted to Billings, 142 miles east, on Friday afternoon. Mockel said the former president continued on to Bozeman on a private jet.

Trump’s campaign released a video of him landing in which he said he was happy to be in Montana, but made no mention of the landing.

The former president came to Montana hoping to clean up some unfinished business from 2018, when he repeatedly campaigned in Big Sky Country and tried unsuccessfully to oust incumbent Democratic Senator Jon Tester.

Tester has tried to convince voters that he is on Trump’s side on many issues, repeating a successful strategy from six years ago. While that worked in a year without a presidential election, it faces a more critical test this fall: Tester’s opponent, former Navy SEAL Tim Sheehy, is trying to link the three-term incumbent with Democratic presidential candidate Kamala Harris.

Harris benefited from the enthusiasm of her Democratic electorate nationwide, which quickly rallied behind her after President Joe Biden withdrew from the campaign last month. She drew large crowds in swing states and toured this week with Minnesota Governor Tim Walz, her preferred running mate.

Trump’s only campaign this week will be in a state he won by 16 percentage points four years ago, rather than a contested November seat. Facing new pressure from a candidate with growing enthusiasm in the race, Trump on Thursday called questions about his lack of swing-state stops “stupid.”

“I don’t have to go there because I run those states,” he said. “I go because I want to help senators and congressmen get elected.”

He will make additional donation stops in Wyoming and Colorado.

Trump could be decisive in the Senate race in Montana

Friday’s rally at Montana State University, scheduled to begin at 8 p.m. Mountain Time, is expected to draw thousands of GOP supporters. But the former president’s greater impact may simply be having his name ahead of Sheehy on the ballot in November, said University of Montana political analyst Rob Saldin.

“There is a part of the electorate that will go to the polls if Trump is on the ballot,” Saldin said. And that could benefit Sheehy, a Trump supporter and newcomer to politics who made a fortune with an aerial firefighting company.

Republicans have been successful in Montana for more than a decade and now hold all state offices except Tester’s.

Tester has won his previous Senate elections by a narrow majority. He presented himself as an open farmer who builds personal relationships with the people of Montana and is willing to distance himself from his party on important issues. He is also successful in collecting donations.

The race has drawn national attention because Democrats hold a razor-thin majority in the Senate and have been able to defend far more seats than Republicans this year. Tester is considered one of the most vulnerable Democratic incumbents.

For him to win, many Trump supporters would have to vote split and support the Democratic senator.

Trump’s push to oust Tester dates back to the congressman’s work as chairman of the Senate Veterans Affairs Committee in 2018. Tester exposed past misconduct by Trump’s personal physician, Ronny Jackson, that derailed Jackson’s nomination to head the Department of Veterans Affairs.

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

Tester has distanced himself from the national Democrats

Before Trump’s recent visit, Tester tried to hedge against accusations that he was part of the Democratic establishment by naming Republicans who support him, including former Montana Governor Marc Racicot. His campaign highlighted more than 20 bills, many on veterans issues, that Tester had introduced and Trump had signed.

Tester was also the only Democratic delegate from Montana who did not cast a vote for Harris as the party’s presidential nominee after Biden withdrew. And when the Democratic National Convention is held in Chicago later this month, Tester will be back in Montana “to farm and meet the people of Montana in person,” said campaign spokesman Harry Child.

The last time Tester attended the Democratic National Convention was in 2008. That was also the last time a Democratic presidential candidate came close to winning in Montana. President Barack Obama lost the election by just over two percentage points.

A similar situation is developing in Ohio, where three-term Democratic Senator Sherrod Brown faces a tough election campaign. Voters in the state are expected to vote for Trump.

Harris visited Ohio when the two were Senate colleagues to raise money for Brown’s 2018 campaign, but Brown has said he has no plans to campaign with her this year. Like Tester, Brown has pointed to legislation he helped write that Trump signed.

Friday’s rally will take place in Gallatin County, which Tester has increasingly relied on throughout his political career.

He lost the district in his first Senate race in 2006, but his support has grown since then. A decisive victory in Gallatin in 2018 helped him win over Rosendale.

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

Seifert endorsed Trump in 2016 and said he continues to support other Republicans, including Montana Governor Greg Gianforte and Senator Steve Daines.

“Montana residents are voting for the person rather than the party,” Seifert said. “For the state of Montana, Jon is the person who can do what we need.”

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

Tester has raised more than three times the amount in campaign contributions reported to the Federal Election Commission. However, outside groups supporting Sheehy have helped the Republican make up much of that shortfall. Campaign spending is expected to exceed $200 million as Montana’s airwaves are flooded with advertising from both sides.