Nothing like this steady stream of former staffers coming out against a president has ever happened before. Don't expect any direct effect, but as with cross-party endorsements by politicians it has indirect effects. https://twitter.com/AaronBlake/status/1306685651484639232

Indirect effects: (1) Each time it happens at a high enough level it's a story, which doesn't last long but it's a bad-for-Trump story that bumps any potential good-for-Trump or even neutral stories.

(2) There's surely a cumulative effect on "neutral" journalists. Their strong instinct is both-sidesism; these defections make it more clear to them, and "safer", to treat Trump's unfitness for the job as an objective fact, rather than trying to stop themselves from doing so.

Recent column on it here: https://www.bloomberg.com/opinion/articles/2020-09-08/will-republicans-for-biden-change-any-minds?sref=rMMJuv3g