Unvetted Walz a sign of Harris ineptitude

Tim Walz was clearly not vetted properly before being chosen as Kamala Harris' running mate.  As bad as Walz is as a VP nominee, the two main things this points out are about not about Walz but about Harris herself.

Walz had issues that Harris did not discover, or else think were a problem. Clearly the campaign miscalculated.

The two takeaways:

1. The pick was primarily political so as not to be Josh Shapiro since he's Jewish and she doesn't want to alienate her pro-Palestinian 'supporters'.
2. Walz was not properly vetted and that's a clear sign of a shallow candidate, which will ultimately lead to a shallow administration.

How does something like this sneak through the vetting process, unless the vetting process itself is epically flawed or weak?