I agree that if you reject this assumption, and instead assume that there are 'diminishing returns', then the conclusion I arrived at could be wrong.
There probably is some kind of diminishing return effect, but we don't know how strong it is. It could be weak compared the the effect that 'readers will consume whatever journalists write'. It's pretty interesting the all of the last four leading candidates (Trump, Cruz, Clinton, and Sanders) all had roughly comparable numbers for pageviews per post. That's evidence that readers just pretty much read whatever is published (with the exception of Kasich, a long shot).
It's also true that if you're a journalist right now, faced with the current distribution of articles, you're likely to get more page views by writing your next article on Clinton. This claim doesn't rest on any strong assumptions. That could change if many more articles on Clinton are written, but it's true for now.
If you look at the data in the dashboard, it's also interesting to see that Bernie Sanders gets way more social and search referrals compared to Clinton and Trump.