I've given all my reasons for skepticism about this morning's vice presidential pick. Now that Mitt Romney has chosen Paul Ryan, let's focus for a moment on the positives.

• Ryan brings relative youth, exuberance, and intellectual heft to the Republican ticket
• The potential, at least, exists to have our first serious discussion of entitlements at the national level
• Ryan has proved himself to be the best spokesman for conservatives on entitlement reform
• Romney was going to be attacked for the Ryan Medicare plan anyway; now he has a running mate who can defend it
• Ryan has a strong pro-life record; the swing voters in this election aren't necessarily social liberals
• Conservatives now have a larger stake in electing the Republican ticket, not just defeating Barack Obama
• This is the first time that the naturally risk-averse Romney has shown any inclination toward potential game-changers

Two big challenges remain: Adding Ryan to the ticket doesn't obviate the need for Romney to push back against the Obama campaign's definition of him; Team Obama is going to move just as aggressively (and predictably) to define Ryan in a negative way. Look for lots of old ladies being pushed off cliffs in the coming days.