Commerce and let him be the new Wilbur Ross? But I think the question is what you perceive as “valuable.” Cabinet Secretaries are certainly more “powerful” than the comms shop folks, but aside from two or three positions they’re largely forgotten and no one other than DC wonks even know who they are. If you view Vivek’s primary strength as articulating Trump’s message, he’s actually probably more valuable in one of the public facing spox type roles than he is in a substantive role.
He’d be best in DHHS and working to improve ACA. But he probably wants to do something more splashy like fitting his head through a door. JK. He’s probably more normal and could be good at something like HUD. He’d be able to figure out what Ben Carson was doing.
