He found his passion there, earned a doctorate in social psychology in 1985 at Princeton, and has since won a Guggenheim Fellowship and the Phi Beta Kappa teaching prize for his work at Harvard.

Unlike Mr Karzai, he has campaigned across the country, rallying Afghans and offering them ideas—some good, some bad—on how to solve their problems.

It will also worsen Afghanistan's main ethnic division between Pushtuns, Mr Karzai's group, and a powerful Tajik minority who voted mostly for Dr Abdullah.