Yes, it's legal to have quid pro quo in campaign donations. And politicians take contributions in exchange for their time all time the time. Every political fundraising dinner is almost exactly analogous to the Wu car ride fundraiser.Is it legal to offer a service in return for a campaign donation, since the whole thing isn't tax deductible anyway?
If you want to be extra careful in this instance, I guess you can mark the gas as a campaign expense, but it's probably not necessary.
As others have stated, this is a remarkably tone-deaf fundraiser. I've seen a lot of really clever ideas to raise money for political campaigns as well as a lot of bad ideas. This is the worst I've come across. Wu clearly came up with this on their own. No professional political operative would ever, ever, ever suggest mentioning the words "my Porsche" in any context, especially where it's published online for the world to see.
This whole idea is just fucking idiotic.