It is fanciful to imagine that a run-off election, or even forcing Mr Karzai to share power with his former foreign minister, will substantially improve the prospects for victory in Afghanistan. From a security perspective if nothing else, trying to avoid the run-off seems more sensible.
The Economist is almost as pessimistic:
The outlook for a successful second round is so bleak that most analysts believe it will in fact not take place at all. Some still cling to the hope that Mr Karzai and Dr Abdullah will make peace and form a coalition government, though both men have ruled this out. Or Dr Abdullah might withdraw in return for promises from Mr Karzai about enacting the constitutional reforms he wants, which would take power away from the presidency. That might indeed warrant praise as a piece of statesmanship.