Tim Walz is a bad choice for VP for all the same reasons that J. D. Vance was a bad choice for VP. Walz gives Harris no voters that she didn't already have. Even worse, Walz is the governor of a very safe blue state, Minnesota, so he doesn't give her a state that she didn't already have locked up. At least Vance boosts Trump's chances of winning the key swing state of Ohio.
Both Harris and Trump failed to pick a VP candidate who expanded their appeal beyond their base. Harris's choice is the worst of the two picks because Vance increases Trump's odds of winning Ohio. Minnesota has not voted for the GOP nominee since 1972.
Oh, Mormon Mike, did the cult totally scrub your brain? OH hasn't been a swing state since Obama. (And there really weren't Swing states because Obama beat McCain and Romney handily.)
First and foremost, Veeps are rarely chosen for Swing state status. Let's review, shall we?
Harris - CA was not a swing state.
Pence - IN was not a swing state.
Kaine - VA was marginally a swing state, but not really. GOP hasn't taken it since Bush in 2004.
Ryan - WI was a swing state, but Romney still lost it.
Biden - DE, definitely not a Swing State
Palin - AK not a Swing state.
Cheney- WY not a swing state
Edwards - NC was marginally a swing state, but the Dems still lost it.
Lieberman - CT not a swing state. (That guy acted like he was the Senator from Israel, anyway!)
Usually a VP is picked on the following criteria.
1) Do they make up for an area that the President lacks. - Walz does in that he appeals more to rural voters. Vance really doesn't appeal to anyone who wasn't already drinking the bleach.
2) Are they someone you have reasonable confidence could take over in case the president dies? - Walz- No problem. Lots of experience. Vance- Hasn't even been in the Senate for two years.
The third factor is "Impeachment/Assassination Insurance." No one is going to want to remove that guy if the other guy is the alternative. Only a few Veeps fall into this awful category, like Dick Cheney.
Walz is a particularly good choice because the man is so likable. The Couchfucker (No, no, we call him the Couch Lover in front of the children) is just weird and creepy.