Biden gave the game away when he jumped on Ryan for daring to mention Kennedy (apparently trying to channel Lloyd Bentsen scolding Dan Quayle). Ryan was merely making the point that keeping tax rates low actually raises revenue when the economy improves and more people are working. Biden shaking his head and muttering “it’s never been done”, despite the abundance of evidence to show that it has, made for a weak counterargument. The “so now you’re Jack Kennedy?” outburst made Biden look small and desperate - but then, his whole performance did that, too.
And, of course, the irony is that Kennedy was as much a media created fraud as Obummer is.