Gosh, I feel like an alien when it comes to the subject of Collin Peterson. His race is a tossup, pure and simple, same as it was in 2018, 2016 (arguably a much more dangerous year for him), and 2014.
He's probably more likely to lose now than he ever has been, but there's no reason to think he is overall likely to lose, let alone sure to lose.
There was PLENTY of reasons to believe he was likely to lose, which he did by 13 points, larger than any Republican incumbent's loss in 2018. The fact the he did
worse in 2018 than 2016, when almost no other Democratic incumbent did, should've been the first warning sign. Then, you add in the presidential year straight-ticket voting and polarization (Peterson won in 2016 because the congressional Republican coalition wasn't nearly as reconciled with the Trump coalition as 2020) and a reputable opponent, it was clear he was an underdog.