How the heck do I manage to end up agreeing with Justice Thomas? (and to some degree Roberts)

I've now read the opinions in McCutcheon vs FEC and I don't get it. The plurality opinion says that aggregate contribution limits don't stand, but individual caps do. The logic of this escapes me.

Thomas, in partial concurrence, would overturn individual contribution limits. I disagree with him in principle, but I find his logic coherent. I think that the plurality (Roberts, Scalia, Kennedy, Alito) are trying to split the baby and the result is a bloody mess.
( Herewith legal/political wonkery most people don't care about )

I expect I'll read more analyses in the coming days and may come to see what the Justices think they're doing here, but right now I don't.