I'm glad you asked.
One, Montana went for Trump by 21 points in November. Gianforte ran and won by 7. That was a huge swing away from Trump, but it wasn't quite enough for Democrat Rob Quist to get the win. It should still worry the hell out of the GOP though. 13-14 point swings towards the Dems in the generic Congressional ballot means a huge Dem takeover in November 2018 if that holds.
Two, Libertarian Mark Wicks got 6% of the vote. If Wicks wasn't in the race at all, this would have been much closer. Yes, Quist still would have lost as Gianforte got more than 50% +1 of the vote, but it would have been a 2-3 point win rather than 7-8. And that would have been a complete shocker. If you assume that Wicks got a healthy amount of anti-Gianforte votes that would have gone to Quist, Wicks definitely helped Gianforte.
Three, Dems gave up on this race far too early.
While we are all talking about #Montana here is a chart that shows you a breakdown of outside spending in this race. pic.twitter.com/0tKoFiIdx8— Adam Parkhomenko (@AdamParkhomenko) May 26, 2017
C'mon. Quist was outspent almost 10-1. And yet when Dems chose to spend money to help Dem Gov. Steve Bullock win re-election and stayed competitive on campaign spending, Bullock was able to beat Gianforte by 4 points even as Trump got a 21 point win in the state.
Dems abandoned Quist, period. The money wasn't there. The GOP money was and they won. By the time the Dems realized they had a race on their hands, the GOP upped the money they spent on it again.
Yes, it cost the GOP $5 million to defend Montana's at-large House seat. But they won.
Here endeth the lesson.