It has been widely discussed how counter-productive the anonymous op-ed was on its own terms, since few things could be better calculated to bring out Trump’s worst instincts. It also surely hurt what must be the author’s own agenda of stamping out Trumpism in the GOP. It’s not helpful to that cause to have portrayed one expression of the internal party opposition to Trump as a cabal that is self-servingly disloyal and to brand it as the resistance, with its inevitable association with the left-wing hysteria about Trump. If the president runs again and loses in 2020, there will be loyalists of his who will say that he was stabbed in the back, and one of them — perhaps Don Jr. — will probably run in 2024 on this theme. The op-ed can only buttress that argument.
(By the way, my current theory is that the author is someone on the national-security side with neo-con-ish views and, obviously, a real fondness for John McCain.)