The Economist has a thoughtful interview with Reihan. His thoughts on Paul:
My suspicion is that non-interventionism is going to enjoy a rebirth among conservatives. As memories of 9/11 fade and casualties continue to mount, a desire for an independent foreign policy with an inward focusI won't call it isolationismwill reassert itself. Though I'm a firm believer in a more forward-leaning foreign policy (my instincts are more McCain than Paul), this is a good and healthy debate to have. So in that sense, Mr Paul is good for the party. I worry, however, that the Paul movement represents a turn from political realism.
Call me unprincipled, but I'm very confident that America's federal government will never return to its pre-New Deal state. And so having a large and vocal faction of the GOP that advocates dismantling the New Deal, the Great Society, the Progressive Era, and that's uncomfortable with Abraham Lincoln's Yankee Leviathan is not going to win over swing voters or contribute much to a 21st-century governing agenda.
All that said, the Paul movement is incredibly diverse, and his "Campaign for Liberty" has energised moderate libertarians as well as goldbugs. Overall, I'd say Mr Paul is a slight net positive.