He likely would've lost his own Clinton +3 district last year, so it's hard to see him winning statewide. On the other hand, WA is a lot more friendly to Republicans on the gubernatorial level. On the other other hand, he'll be sharing the ballot with Trump.
I could see him reaching McKenna levels I guess, but probably not. Unless Inslee damaged himself with the botched presidential run, last time I checked his approvals were pretty decent.
Republicans literally haven't won a gubernatorial election in Washington in 40 years. Reichert is DOA.