At this point, if there is any potential for an Obama nominee to be blocked, it would be the nomination of Eric Holder as Attorney General.
The obvious reason, of course, is the unpardonable pardon of Marc Rich.
A blogger at the liberal DailyKos writes:
"Two days ago, knowing that there was a Karl Rove-led effort to "go after" Attorney General nominee Eric Holder, Patrick Leahy inexplicably agreed to a Republican, request for more time to "prepare" for Holder's confirmation hearing."... What might explain why Leahy "inexplicably" did this? Don't forget, Leahy was very critical of the Marc Rich pardon...