Big doings in Iranian politics - Khatami's out

(Reuters) "Iran's moderate former president Mohammad Khatami withdrew on Monday... "He has decided to withdraw ... but he will back another moderate candidate who will be announced shortly in a statement by Khatami."

This is being spun as Khatami uniting the reformist vote, but my understanding was that Khatami was the leading reformist vote getter. So ?????

(Maybe Khatami isn't acceptable to Khamenei and the ruling clerics? ...said they'd back Mousavi, but not Khatami...?)