General Discussion

merely incidental.

Clinton/Gore leaned into two Southerners.
Bush/Cheney were effectively both Western candidates — Cheney even had to re-establish Wyoming residency because they were both tied to Texas.
Obama/Biden had geographic variance, but Biden wasn’t chosen for Delaware.
Trump’s VP selections weren’t about geographic balance either.
Biden/Harris and Harris/Waltz may have produced some geographic diversity, but it’s a stretch to call that the organizing principle.

The broader pattern is that VPs only tend to matter electorally when they’re actively harmful, like Pailin. Otherwise, they’re marginal to outcomes.

I don’t see why a California/Arizona ticket is uniquely problematic. Newsom/Kelly may turn out not to be the optimal ticket, but it won’t primarily be due to geography.