We can say with a high degree of confidence that Mitt Romney’s vice-presidential pick has largely come down to three men: former Minnesota Gov. Tim Pawlenty, U.S. Sen. Rob Portman, and House Budget Committee Chairman Paul Ryan. And it’s more than possible that Romney has already made up his mind. All three VP finalists bring something different to the table. Pawlenty is the loyal outsider, who would enable a Romney-Pawlenty ticket to run as former governors vowing to take on Washington; Pawlenty also potentially would add some blue-collar appeal to the ticket. Portman would be the insider, someone who knows the ways of Washington and who could help govern starting on Day 1. And Ryan would be the crusader, who wants to substantially transform America’s entitlement programs and who would excite a good portion of the GOP’s conservative base. Indeed, Ryan has emerged a VERY REAL possibility, but he also brings the most risk. If Romney selects him, it’s more than conceivable that the dominant campaign discussion in the fall won’t be the economy — but rather the deficit and Medicare. Of course, there was already a good chance the Ryan plan will get plenty attention regardless of Romney’s VP pick…

Just how important could the debate over the Ryan budget, especially if he’s Romney’s VP pick? Just consider this AARP poll of voters over 50, in which Obama and Romney are tied 45-45% with the group (and with Obama’s approval at just 42%). Per this poll, 91% believe “Social Security is critical to the economic security of seniors” and “the next president and Congress need to strengthen Social Security so that it is able to provide retirement security for future generations.” (That includes about three-quarters of Romney voters.) And on Medicare: 95% say “Medicare is critical to maintaining the health of seniors” and 88% say the next president and Congress “need to strengthen Medicare so that it is able to provide health coverage in retirement for future generations.” The poll was conducted by Hart Research and GS Strategy Group. (Disclosure: Hart Research is the Democratic half of the NBC-WSJ poll.)