The announcement comes a few days after Sen. John Walsh (D), the previous nominee, said he would drop out of the Senate race in the aftermath of a scathing New York Times report that said he plagiarized a large chunk of his master's thesis.
Democrats now have to move quickly to pick a new nominee.
The special convention will be on August 16th at 9 a.m. at 98 West Custer Ave, in Helena Montana.
"We look forward to bringing together Montanans from across the state to select our Democratic Senate nominee. As we move through this process, we must remember this election is not about any one candidate; It’s about ensuring our public lands aren’t sold off to the highest bidder, women are free to make their own health care decisions, every Montanan has the opportunity to succeed, and our kids and grandkids are not denied quality education," Montana Democratic Party Chairman Jim Larson said in a statement.
After Walsh announced his decision to not run, former Gov. Brian Schweitzer, one of the most high profile Democrats in Montana, said he did not want the nomination for U.S. Senate.
Whoever Democrats select will face Rep. Steve Daines (R-MT) in the general election.
Daines has been the frontrunner throughout the race.