Political ads? Campaign ads?
Newspapers advertising that they've got the fastest election news?
People looking for an apportionment calculator are likely interested in a past or future election and interested in political topics. That's a lot of potential ads you could show.
So if there us the value you suggest, it should be an easy sell. Probably less work than he went to to tweak the site.
Then again, are people investigating vote targets undecided voters? And good luck getting media to advertise....
But even on YouTube it's back nowadays, most YouTubers get their money from sponsorships which work just the same as old-school pre-internet ad placement.
But seriously, there are plenty of ads that are based on geo located IP. Then of course there’s the cookie (and cookie replacement) ads.
Complaining about site content is pretty bogus.
But, as a thought exercise. Let's say you were selling ads directly to the business paying. Which businesses do you suppose might be interested on a congressional apportionment calculator?