The reduction in coverage was most pronounced before primary elections.

The reduction in staff covering politics made it harder for voters to differentiate between moderates and extremists in partisan primaries, and allowed extreme candidates to do better than they did before.

This makes sense, and it explains a lot, actually.

And to be clear, it’s not just craigslist as a culprit here, but it’s such a controlled A/B test that the effects are reliably measurable.

In the original paper, they also observed reduced turnout for House/Senate elections (which the article didn’t emphasize as much, but is defininitely there): https://academic.oup.com/restud/article/92/3/1738/7665573?login=false#517516514