It's not at all crazy to imagine laws that simply limit the total amount of money spent on a campaign, regardless of where it comes from.

What if he just makes a feature film about himself and gives out free tickets? I don't see that there is such a clear distinction between a campaign and other speech.

Well, answering those questions is precisely the goal of campaign finance regulation.

In Canada, campaign finance rules put limits on how much one can spend on their own campaign. The limit is higher than the limit for donating to other people's campaigns, but at 25k CAD, it is nowhere near enough to enable billionaires to buy elections or have unfair advantage. When a Canadian multi-millionaire reality TV star ran for conservative party leadership position, this happened:

https://globalnews.ca/news/3984252/kevin-oleary-conservative...

One would assume that any comprehensive campaign finance rule would have similar provisions.

For a candidate, I can only donate $2800 towards primary election efforts, and $2800 towards a general election effort. Bloomberg, any candidate, should be prohibited from spending any more than that on their own campaign, billionaire or not.

One of the downsides to that rule, is that it heavily favors incumbents who have big donor networks in place. And it imposes a big cost on the new players, just to get the donor networks.

It's one contributing reason why it often takes a self-funded millionaire/billionaire to unseat them - or get real traction in a campaign.

Hence why public funding for candidates is so important.

What counts as a campaign expense? If he buys a new suit for an event he just committed a felony?

No. But if he pays for an entire tech team in Manhattan to run his campaign, he should (under campaign finance regulations). I did a phone interview as a potential candidate with someone on that team because I was curious about their capabilities. Such a team should not exist for a self-funded candidate.