Just to follow up on Jonah’s post, here’s the word from a source at OMB on why Portman’s stepping down:

The upshot; challenge of 14 years of commuting from Cincinnati. He goes home every weekend. So he’s looking forward to spending more time with his family. — has three teenagers. He’ll be here through early August — giving Senate six weeks to confirm [former Iowa Rep. Jim] Nussle — that would provide a seamless transition.

Rep. Jeb Hensarling, whose Republican Study Committee is leading an effort back up Bush’s threat to veto spending bills if they exceed his budget request, said in a statement that he thinks Nussle is a good choice to keep that fight alive:

Having proudly served under Jim Nussle on the House Budget Committee, I am confident that he will continue Mr. Portman’s efforts to restrain spending and maintain the President’s ongoing commitment to work with House Conservatives to successfully veto bloated Democrat spending bills that exceed the White House budget request.