I haven't found an article about this yet. I just heard news reports.
Here's one:
https://www.golocalprov.com/politics/nyt-editorial-board-calls-on-biden-to-exit-race
In a highly unusual move, the editorial board of the New York Times published a Friday night editorial titled “To Serve His Country, President Biden Should Leave the Race.”
Apparently the fact that this Editorial was published on a Friday night is a big deal.