If you say the WAPO would provide the same gratuity to a GOP candidate I wont argue but to me it doesnt look good for objectivity until I see an example of it.
As noted in my last post, it's not a gift from the Wash Post.
Every election primary cycle, their editorial board offers a published recommendation for all major party races.
That's distinct from the later actual election when they will offer a final recommendation selected between the candidates on the final ballot. (Info that can also be used under the Fair Use laws if so desired).
While you may not have seen such use of media endorsements on a yard sign, surely you've many times seen them in television and radio advertising.