Them, and the AP. I pointed out to my kids that the headlines in every paper in the US are the same, day after day after day. Setting aside extraordinary events (man lands on the moon, 9/11 attack, etc.), the probability of all editors at all papers finding the same stories to be "most important" is approximately zero. Therefore, the evidence (same headline story at every paper across the US) shows that the papers are not independent when it comes to choosing what to report and how much importance to attach to each story.
I have also found several instances where AP makes up stories from whole cloth. Literally, fiction being reported as a news event.