It's tempting to wonder how Christmas passed in John McCain's house. It doesn't take much to imagine the atmosphere probably got a little Macbeth-ish at times.

Married to a woman who defied him by publicly acknowledging the connection between anti-gay laws and anti-gay bullying (a point of view that she then sadly and almost wordlessly retracted) there must have been some tense moments in the upscale Arizona mansion.

And consider that as he looked across his well appointed table at his own high profile daughter Meghan, McCain was contemplating yet another betrayal: her ardent support for marriage equality for gays is well known.

He must have feared for the GOP. He must have feared for the future. He may even have feared for himself. As the greatest of all Republican politicians once remarked: a house divided can not stand.

And worst betrayal of all, from McCain's point of view, was the repeal of DADT. Although he hasn't been a member of the US armed forces for decades - and there have been quite a few changes in bootcamp in the interim - he is still consulted as a supposed "expert" on military matters by the media, if no longer by the Pentagon.

So it was sad to see McCain use his platform to search for a legitimate reason to flout the wishes of the President, the military's top brass, the majority of active service members and the American public.

Apparently still enraged by his no-contest loss to Barack Obama, it doesn't seem to take much to tilt McCain over into the red zone these days, as his recent blistering exchanges with his Senate colleagues will attest.

The truth is McCain's personal contempt for the President has turned him into a give-no-quarter Republican hardliner. But it should be remembered that deep personal antipathy is the worst possible guide to enlightened decision making, although we're two years and one Sarah Palin beyond all that now.

When private passion overruns public principle you're setting the stage for tragedy - just ask William Shakespeare. His plays are filled with once noble men surrendering to their baser natures with devastating consequences for everyone in their orbit.

McCain's spectacular acts of fury and sabotage seem certain to continue. But from the outside it's beginning to look like the person they'll discredit most is the man himself.