What do Rick Santorum and Clint Eastwood have in common? Sorry, Rick, you haven’t made it yet as an Eastwood-style make-my-day cultural icon. But in different ways, Santorum and Eastwood have demonstrated the limits of both an entirely negative slant on politics and a pessimistic take on America’s future. Santorum’s Tuesday sweep of Republican presidential contests in Minnesota, Missouri and Colorado was a sharp rebuke to Mitt Romney, the on-again, off-again “inevitable” GOP nominee, who has built his campaign almost entirely on attack