Top Montana Democrats sent a scathing letter to Democratic National Committee chair Tom Perez on Friday in response to the DNC's decision to change its debate qualification rules in a way that would prevent Gov. Steve Bullock, a 2020 presidential candidate, from participating.

In the letter, which was obtained by CBS News, DNC members Mary Sexton, Jorge Quintana and Jean Dahlman said Bullock, the Governor of Montana, "deserves an opportunity to take the debate stage." Bryce Bennett, who resigned from the DNC on May 29th to run for statewide office, also signed the letter.

"We know many consider us to be fly-over country or little more than an ideal vacation spot, but we know we've offered countless invaluable contributions to the Democratic Party and our nation as a whole," the letter says. "The recent implementation of extra qualification rules for the June debates in Miami could deny the Democratic Party a voice representing rural America."

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Sexton, Quintana and Dahlman are the only three DNC members from Montana.

The new debate rule, announced Thursday, disqualifies a Washington Post/ABC poll that was previously included in debate qualification criteria. According to the Bullock campaign, he is the only candidate that will be affected by the change.

The DNC said it excluded the Washington Post/ABC poll because it objected to how the pollsters asked an open-ended question instead of listing of the names of Democratic candidates. To qualify for the Democratic debate later this month, candidates must either have registered at least one percent support in three approved polls or have received donations from 65,000 people, including at least 200 people in 20 different states.

A spokesperson for the Washington Post told CBS News, "In a field this large and at this early stage, we set out to measure which candidates Democratic-leaning voters are supporting, if anyone. An open-ended question was ideal for this purpose."

The Bullock campaign says that the governor's late entry into the race helps his low national polling, and that he waited to get into the race "until he passed Medicaid expansion for nearly 100,000 Montanans."

"Until yesterday, there were three nationally qualified [polls] that everybody was saying count, and then they announced they weren't going to count one," Bullock said Friday in an interview with WBUR, a Boston NPR station.

"If I ever had to choose again between campaigning for 100,000 donors and securing health care for 100,000 people, it's the easiest decision I'll ever make."

DNC spokeswoman Xochitl Hinojosa told CBS News, "The DNC has been transparent all along and made public in December that the debates would start in June. In addition, we notified the Bullock campaign several times beginning in March that this poll would not count because it was open-ended and not a traditional horse race question."