Walz is new. I think they dropped Beshear because they are never going to win KY and even though he's a Southern governor and charismatic, he's younger than Kamala and not particularly well known nationally (yet).
Heavy on governors (expected) and no Mayor Pete (though he's already vetted, so...)
@Cosmichomicide From what I understand Gretchen still has a lot of work to do in Michigan before she can accept the VP role, though I'm sure she would be hugely honored to be considered for the nomination.
She already said she wasn't leaving Michigan at the same time she endorsed Kamala.
She's on the list because she has some national brand and the party wants to expand it.
No chance they run two women in their 50s and Big Gretch really isn't second chair.