i expect we'll never know who really won the afghan election. in any case, i think it will play out like this:
-karzai will claim an outright victory, with no need for a runoff (the idea his people are floating now)
-abdullah abdullah, and a bunch of other opposition people, will cry fraud and try to stir up an iranian style protest.
-it won't work.
-the u.s. will mostly stay out of it, which effectively means karzai will get another term. i don't think the obama administration is as wedded to karzai as the bush administration was. but they also don't seem to mind karzai and to stir the election fraud pot is only going to make obama's afghan troop escalation more complicated. so they'll let any doubts about the election go.
