ow will the 2012 debates rate in the campaign history books? Lots of political drama — but not a single breakout one-liner.

Sure, Internet wags had fun with Mitt Romney's comments about Big Bird and "binders of women," but neither will likely have the staying power of Lloyd Bentsen's devastating riposte to Dan Quayle in 1988: "You're no Jack Kennedy."

With the millions and millions spent on presidential campaigns, you'd think the candidates would be able to deliver a zinger that perfectly captures the moment — but it's harder than it looks.