HELENA, Mont. (AP) — It didn't take long for the fallout to begin after Gov. Steve Bullock announced he was going to seek the Democratic nomination in Montana's U.S. Senate race to challenge Republican Steve Daines.

Three candidates from Bozeman, including fundraising leader Cora Neumann, withdrew from the race — saying Bullock offered the best chance to defeat Daines.

Neumann, who raised $650,000 during her five-month campaign, withdrew from the race Monday morning.

“I know that what matters most is that we come together in the effort to beat Senator Steve Daines," Neumann said in a statement. “That is why I am withdrawing from the Senate race and throwing my support behind Governor Steve Bullock."

Mike Knoles, a physicist and mathematician, tweeted Monday morning that he was dropping out.

“This race is too important to let my ego dictate decisions,” Knoles said. Steve Daines “must go, and I will do everything I can to make sure we #FlipTheSenate.”

Last week, as speculation grew that Bullock was considering a run, Democrat Josh Seckinger of Bozeman said he was ending his 16-day campaign to endorse Bullock.

The other Democratic candidates are Liberian refugee and Helena Mayor Wilmot Collins and Navy veteran and energy field engineer John Mues of Loma. Collins said Monday morning he was still a candidate. Mues' phone went unanswered when an attempt was made to reach him for comment.

Daniel Larson, a hardware store manager from Stevensville, and John Brian Driscoll of Helena, have filed election paperwork to challenge Daines in the Republican U.S. Senate primary.

Driscoll is a former Democratic state legislator who served on the Public Service Commission for 12 years. He made late entries in the Democratic U.S. House races in 2008 and 2014, winning the primary in 2008 before falling to U.S. Rep. Denny Rehberg in the general election.

Libertarian Eric Fulton of Whitefish filed paperwork to run in the U.S. Senate primary last Thursday.

The filing deadline for the June primary is 5 p.m. Monday.

After the Green Party qualified for the ballot on Friday, Wendie Fredrickson of Helena filed paperwork to run in the U.S. Senate race and John Gibney of Hamilton filed for the U.S. House race.

The Montana Green Party denounced Gibney's candidacy for a state House seat in 2018 after he refused to back away from statements he made at an anti-refugee protest in Missoula in 2016 that the party said were bigoted.

The Montana Green Party posted on its Facebook page last week that it will disavow candidates running the the U.S. House and U.S. Senate races who call themselves party members unless they have conferred with the party and its promotion of a “progressive, green, corporate-free platform.”

Robert Barb and Joshua Thomas, with a campaign address in Billings, filed paperwork to run for governor and lieutenant governor in the Green Party primary.

It is still unknown who paid for the signature gathering effort to get the Green Party on the ballot. The Green Party has said it did not do so.