Three years ago, Mitt Romney proposed a constitutional amendment that would say "the president has to spend three years working in business before he becomes president of the United States. Then he or she would understand that the policies they are putting into place have to encourage small business to grow."
As Andrew Kaczsynski notes, that provision would disqualify Paul Ryan, who has spent his life working for the government, first as a congressional staffer and then as a congressman.
To be clear about the point here, I think this reflects how dumb Romney's proposed constitutional amendment is, not Ryan's fitness for the presidency. It also reflects Romney's tendency to take positions strategically without carefully considering their long-term impact. When he made that comment, was it really so difficult for him to imagine naming a vice president without business experience? That would, for instance, disqualify career military men, like Gen. David Petraeus.
Update: Some have argued that Romney isn't quite "proposing" this amendment so much as speaking favorably about it as a concept. I think that's a fair distinction. Either way, the basic point is unchanged. A few years ago, Romney thought it was politically useful to say that all presidents should have at least three years in business. But his vice presidential nominee -- that is to say, the single person, aside from himself, who he thinks most qualified to be president -- has not spent three years in business.