Recent spending in CA (Sep 1-now) looks like it's heavily landlord associations running ads against prop 33, which would allow for new rent controls.

https://adstransparency.google.com/political?region=21137&to...

As a CA voter I find it very awesome that I could look that up so easily.

EDIT: The sort order isn't part of the URL, so you have to sort by Amount spent: high to low -- blew that one Google!