Earlier this year, the Montana Democratic Party sued to remove the Green Party from the ballot. The state and federal courts ordered the removal of the party in August, even though everyone agreed it had enough valid signatures in March, and even though it was given its own primary in June. The removal was accomplished by the Democratic Party asking people who had signed the petition to put the party on the ballot to remove their names. Only 600 people removed their names, out of over 13,000 signatures that had been submitted, but that was enough to remove the party because it lost its needed signatures in one state house district, and the state has a difficult distribution requirement for the statewide party petition.
The Democrats were motivated to take this action because they hoped to elect Governor Steve Bullock to the U.S. Senate. But Bullock lost to incumbent Steve Daines by ten percentage points. See the results here.
The 2018 Green Party lawsuit, challenging the distribution requirement, is pending in the Ninth Circuit. The distribution requirement is unconstitutional based on a U.S. Supreme Court precedent, Moore v Ogilvie, that distribution requirements must be equal. The Montana requirement is not. In some districts as few as 55 signatures are needed; in others 150 are needed. Therefore the voters of some districts have more clout than those in certain other districts.