HELENA, Mont. (AP) — Lewis and Clark County Commission Chair Susan Geise has announced she will run for the U.S. Senate race as a Libertarian Party candidate after serving as a Republican because of differences with the Republican Party leaders and concerns about the toxicity of partisan politics.

Geise filed Wednesday as a Libertarian after formerly serving as the chair of the Montana Republican Party in the 1990s, the Independent Record reported.

Geise was selected by the Libertarian Party on Tuesday to replace Eric Fulton of Bozeman, who withdrew on the last day of the regular election campaign filing period, meaning the party had until Wednesday to nominate a replacement candidate, she said.

Geise told the Independent Record that she was concerned by allegations that Fulton was linked to the Republican Party and his dropping out was a political move to prevent the Libertarian Party from fielding a candidate.

“I have read the allegations, I don’t have any facts about it and I hope that’s not true, that this individual was a Republican and it was maybe a tactic, or what I might call a dirty trick, so that suddenly the Libertarians would have no one,” she said.

Fulton previously ran as a Republican for the Legislature, but said in an email he chose to withdraw after Democratic Gov. Steve Bullock entered the race to challenge incumbent Republican Sen. Steve Daines.

“We proudly support President Trump and Senator Daines, as do a majority of Montanans, because we can count on them to preserve our freedoms and liberties and protect our treasured way of life," Montana Republican Party spokeswoman Brooke Stroyke said in a statement.

Green Party candidates Wendie Fredrickson of Helena and Dennis Daneke of Lolo are also running for the Senate seat.

Geise served as a Republican on the commission since 2013, but recently attempted to make the commission elections nonpartisan in the future. She also was a state lawmaker representing Great Falls about 30 years ago.

“I want to be very clear, the Republicans and I have been unhappy with each other for a very long time, certainly since the 2016 election,” she said. "I have elected dozens and dozens if not a hundred Republicans to elected office. I have invested my life to this and I feel that the Republican leadership profanes what we used to stand for and I can’t stomach it.”