Yes, I think he's got a problem there, because his best chance is the Democrats picking him, but his best fit is with the Republicans, for whom he isn't orthodox enough. If a Democratic president picked him, he'd probably be confirmed: he has enough "non-left" background for bipartisan credibility (a Chicago-school law-and-economics background), but has enough left-leaning positions that at least some Dems shouldn't find him impossible to support. But, he's 72, which limits his appeal as a bipartisan choice. And as a straight Republican nominee has has problems on things like abortion. So I would guess he's not destined for the Supreme Court.