I support this idea whole-heartedly. No-one is a perfect prognosticator, obviously, but some people (koff - William Kristol - koff) are so frequently wrong, and on such a thoroughly large scale, that there should be some kind of resource somewhere in which their levels of stupidity can be indexed.
Maybe we need something like the h-index in academia. The h-index is equal to the number of papers you have with at least that many citations. So someone with an h-index of four has four papers with at least four citations in other works, and at most four papers with five citations or more (my h-index, rather abysmally, is either 2 or 3, I think).
Let's do something similar for political predictions: the p-index, equal to the number of mistakes you've made at an equivalently bone-headed level (working out the bone-head scale is the tricky part).
I also think McCain's ignoble display on the subject of DADT is a good place to start. Whilst vile and scabrous turds like Rick Santorum rely on "logic" to vomit their contemptible bilious swill across American politics ("Treating a minority like they're the majority is granting them special rights!"), McCain's ilk prefer to tie their miserable bigotry to actual testable hypotheses.
In the last three years, we were told that the US military couldn't work with DADT gone because the American forces work differently to all those allied countries who got rid of such policies without consequence, which was a little insulting to the US allies McCain et al are usually so keen to pay lip-service to. Then we were told that the problem is that gays can't keep their hands to themselves, which was insulting to homosexuals, and that the military would be unable to maintain discipline, which was insulting to the military itself (nice going guys). As a final, last-ditch effort, the argument was then switched to a fear that recruitment would become impossible, which at a time of double-digit employment, is pretty much insulting to fucking arithmetic.
Much as I give the American press a hard time, I don't think it should necessarily be their job to demand explanations for every mistaken prediction. Life's too short, and we've all been wrong at least once (with the possible exception of Paul Krugman) - my predictions regarding the midterms alone should guarantee a place on the board of shame somewhere.
But the next time John McCain opens his freakishly wide mouth to tell the people what calamity will befall the military if they fail to do exactly what he says they should do (bombing Iran, probably), someone should possibly have the presence of mind to ask whether we can avoid said catastrophe by deploying an elite unit of all those gay soldiers McCain swore on his soul would destroy the armed forces as we knew them.