Edwards’ affair might not have ruined his career - may have set it back temporarily, but I’m not sure it would have ruined it.
What completely ruined Edwards for me (and I wasn’t a fan before, just to be clear), was his denial of his own child, as if that child were nothing. Ick.
True, Eliot Spitzer made a fairly quick comeback. But Edwards is hated, whereas Spitzer, Sanford, Craig, Vitter, Cinton, et al. were mostly just mocked.