Why is the Montana At-Large Congressional seat in play? The Cook Political Report has it at "lean Republican" (R+11), but it's an open seat. The Republican who won a special election there in 2017, Greg Gianforte, and who then promptly beat up a reporter from The Guardian and was convicted of misdemeanor assault, has moved on to run for Montana governor (and maybe beat up a different reportorial demographic).
The Republican on the ballot there this November, Matt Rosendale, won a crowded congressional primary. He has considerable public service to his credit, including one term each in the Montana House and Senate and a term as Montana's auditor. But he also trails a string of high-profile electoral defeats. He was beaten in the 2018 senatorial campaign by incumbent Democrat Jon Tester. In 2014, he ran for the Montana At Large House seat in the Republican primary and came in third. He's very familiar to Montana voters, which in some cases may hurt as much as it helps.
A bigger reason the Montana race is being watched for a possible red-to-blue flip is the overall erosion in the Trumpist Party as both voters and office-holders have grown weary of the Twitterman chaos:
Of the 241 House Republicans in office when Trump was inaugurated in 2017, only 126 (52 percent) are still running for reelection this fall. Incoming GOP members have run on a primary theme of fealty to Trump, with a few exceptions — such as Peter Meijer (MI-03), a self-funder who has run on his military service and barely mentions the president.
Republican Matt Rosendale, who looks old and whose TV spots don't do a thing to dispel that image, is highlighting Donald Trump's endorsement as boilerplate, but as with every other public hugging of Trump by a Republican candidate in this plague year, we have to wonder how much it helps or hurts, even in Montana.
Democrat Kathleen Williams
She's clearly running as a "moderate," but she "fits" Montana and she doesn't strike me as someone who's gonna go DINO on us (I'll be permanently deleting this post if she does). She also has a long record of public service. She served multiple terms in the Montana House, and she ran against incumbent Greg Gianforte in 2018, coming within 4.7 percentage points of beating him. I don't know what her TV spots in 2018 looked like, but I find her not just feisty but appealingly feisty in 2020 (although I do flinch a little that she admits voting for Reagan -- does that look like pandering in Montana?):