"As long as someone else did the same thing or something worse, my candidate should not be held responsible for what s/he did or didn't do."

I think that was first put forth as a political principle by a Greek in Athens in the 5th Century B.C.E.

All politicians and their advocates love to trot it out when their candidate is caught screwing up, with his hand in the cookie jar, in the wrong bed, or making a bad decision, though.