Supposedly almost all scenarios for Romney to win the election require that he win Florida, so it seems less than ideal to a VP who puts medicare and social security cuts in the media spotlight. Perhaps the campaign is underestimating the degree that voters will care about a VP's budget proposals, or overestimating their ability to emphasize wonkish details over "optics". Perhaps the plan is to use the fundraising boost Ryan gives with big donors to drown out Obama's message on these issues.

Another possiblity is that Romney thinks an imminent confrontation with Iran will make make that discussion take a back seat to questions about Israel. Jews are only 3.4% of the population of Florida, although probably a somewhat higher percentage of likely voters. What makes the Iran issue especially important there is that the Jewish voters in Florida are disproportionately retirees and therefore some of the same people who otherwise care about social security and medicare. Any crisis involving Iran, whether it involves an attack or not, could take the pressure off of Romney on medicare cuts since voters rightly or wrongly perceive Republicans as being better for Israeli security.

It's noteworthy that there has been an increase in Israeli sabre rattling about a solo strike on Iran that's roughly coincided with the Ryan announcement. Israeli hardliners are aware that the US election gives them an artificial timeline under which it's perceived they might attack, so they're likely to do something to bring the issue to a head even if they don't have the support internally to follow through with their threats. The issue only has to make the news to benefit Romney.

The other significant event that could occur in the next three months is a new financial crisis, or at least enough of a threat of one, to push the issue beyond the business press. One trigger could be a ruling by the German Constitutional Court on whether Germany is allowed to participate in the European Stability Mechanism. They're expected to give an interim decision by September 12, and a "No" could disrupt the bond markets, especially for countries with the highest debt loads. This is all esoteric stuff to the average voter, but Romney presumably has access to good information on these issues along with the right kind of experience to understand the fallout. Even if he's only expecting a 20-30% chance of a newsworthy financial event, that could be enough to make Ryan the best pick in electoral college simulations, as he's perceived (rightly or not) as being a leading deficit hawk.