There is the possibility that his adoption of his children from Ireland was illegal.
Again, so what if it was illegal? Just like millions walking across the border was illegal, but "it's too late to do anything now"; just like it was illegal for the Clintonistas to have hundreds of FBI files in their possession "we have no idea how those got here"; or Obama's campaign website in 2008 (and probably 2012) allowing contributions from anyone, without checking employment, nationality, etc.
I don't think he can be blackmailed at this point over the adoption of his children. Besides, if a problem with the adoption is common knowledge among FReepers, then everybody already knows about it. But, I suppose he could be threatened with the lives of his children. I just don't think he can be blackmailed in the sense of being threatened over the release of certain information.
I honstly believe he's gone Souter, and that the Bushes were hoodwinked by yet another liberal who was allegedly going to be conservative (i.e. neutral) and turned out to be a big wussie lib.