Strange politics in Afghanistan

A very popular governor who had been very far along in his plans to challenge Hamid Karzai in the August election, meets with Karzai, and then suddenly withdraws his interest.

It get weirder when Shirzai reportedly also resigned his governorship immediately after the Karzai meeting, although Karzai reportedly refused the resignation.

So, what could Karzai have presented in this meeting that could have chased this fighter/warlord, and Karzai's only real challenger, not only out of the race, but almost out of all power?

Related: The WaPo looks at the election from Karzai's perspective and finds he's nearing certain reelection status.

Also note the language which makes it sound like the Obama administration isn't really supporting Khalilzad..