The security forces never split, and Juan Cole reports the bad news that's been ignored elsewhere:
Rafsanjani has clearly decided to defer to Supreme Leader Ali Khamenei on
handling the outcome of the elections, and has come out as critical of the crowd
politics and occasional turbulence they produced. As a multi-billionaire and man
of the establishment, he may well have been frightened that the massive street
rallies for Mousavi a week ago signalled a danger to the status quo, which he is
attempting to preserve.
Rafsanjani doesn't want the increased repression of Khamenei and Ahmadinejad, nor potential revolution. Looks like he's chosen sides.
Sadly, change in Iran will likely have to take some time now. Troublemakers in Iran will have the upper hand for a while, and so will potential troublemakers in Israel who want to start a military conflict.