Despite Obama winning Ohio by 3% in 2012 Brown only beat Josh Mandel by 6%. So assuming the GOP candidate in this race isn't like him (very likely) and Trump wins Ohio by 8+ again (probable), it's very tricky for Brown to win.
First of all, Trump isn't guaranteed to be the nominee. He's favored but there's still an opening for a candidate like DeSantis to pull off the upset.
Secondly, Trump (or any Republican) could theoretically win the race by more of a J.D. Vance margin than his 2016 and 2020 margins.
Finally, if Brown runs as much ahead of Biden as he did Cordray in 2018, he wins.
That was 2018, and Cordray v. DeWine was a rematch. So that's really not applicable.
