AP

A few other data points can support some of the themes that have arisen since the Ryan pick. (Note also, we'll have a new ABC News/Washington Post poll result measuring favorable or unfavorable views of the selection, later today.)

Size of government: This is a debate in which the Romney campaign has opportunities. Last time we asked, last fall, Americans by 56-38 percent said they preferred smaller government with fewer services over larger government with more services (see full story here). But, by 70-18 percent, they thought Obama preferred larger government. It's a perception on which he's vulnerable.

Fairness: Obama's pushback to the big-government argument has been fairness, and this does work as a reply. In our polling in May, Americans by 56-34 percent said "unfairness in the economic system that favors the wealthy" is a bigger problem that "over-regulation of the free market that interferes with growth and prosperity." This break with Romney/Ryan/Kemp/Hayek/Mises/ Rand is a counter-vulnerability on the GOP side.

Conservatives: As noted above, Ryan's selection looks like an effort for Romney to shore up support in his base; in our polling last week he had a 65 percent favorability rating from conservatives, vs. Obama's 84 percent among liberals. (To Romney's advantage, there are a good deal more conservatives than liberals in this country; still, he could stand to do better among them.)

Tea Party: Ryan's also said to be a favorite of the conservative Tea Party movement; that, too, could provide a boost in the base, but perhaps prove a detriment elsewhere. Last time we asked, in April, Americans divided on the movement, 41-45 percent, support-oppose. Just 12 percent "strongly" supported it, while twice as many were strongly opposed. And the public by a broad 23 percentage points, 50-27 percent, said the more they hear about the Tea Party movement, the less they like it.

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