More than anything else, Paul and his supporters need to understand that the average voter -- even the average GOP primary voter who is naturally sympathetic to free markets and a less interventionist foreign policy -- is skeptical at their core of radical change, even if it sounds good to them in principle. This conservative disposition is often good for the nation's libertarians. But it applies to the radical changes that Paul proposes just as fully as it does to radical changes proposed by liberals, conservatives, progressives, environmentalists, or socialists.
And rightly so. Presidents don't get to remake society from first principles. The most influential push the country in the direction they think is best, often because a crisis gives them the opportunity. Every president inherits a lot of policies that they wouldn't have chosen, but that they're locked into and must make function as smoothly as is realistically possible. Maybe you think that Social Security should be privatized, or that American troops shouldn't be in South Korea. Even if you're right, getting from the status quo to the ideal policy can be done in countless ways, some of which would prove disastrous. And even the right plan has to be well executed.
One reason I'd be more comfortable voting for President Gary Johnson than President Ron Paul is that I've studied how he governed. In New Mexico, Gov. Johnson inherited a state that looked dramatically different than the one he'd have created if he was inventing things from scratch. But his principled skepticism of certain state agencies didn't result in a dysfunctional bureaucracy or a citizenry suddenly faced with pothole filled streets and garbage collecting on the sidewalks. As far as I know, there is no instance when he let his ideological assumptions trump pragmatism in a way that blew up in his face. Asked by an interviewer, "Why should we gamble on a president with untested ideas like yours?" he can answer, "I'm all about doing what works. I applied my political philosophy in New Mexico, and far from being too radical for its Democratic voters, I was re-elected and left office with approval ratings greater than fifty percent."
Paul has no governing record to invoke. What can he say when asked, "Why should we gamble on you?" His typical answers amount to the following: 1) It's more of a gamble to go with the status quo candidates, because their approach is a proven failure; 2) You should gamble on me because the reasoning in which I ground my policy arguments is persuasive on paper.
Those answers aren't enough to win the GOP nomination or the presidency. Risk averse voters sympathetic to many of Paul's ideas need to be reassured that he'll constantly test his ideas against reality, that he'll be cautious and skillful as he transitions from the status quo to the America he'd like to live in, that he'll surround himself with some advisers who are constructively skeptical of his ideas (especially on monetary and foreign policy, because that is where he is most certain of himself). Can he hedge bets like a pragmatist who is painfully aware of human fallibility, rather than staking everything on his ideological presumptions? And how will he do all of that without abandoning the principles that are the source of his growing appeal?
These are the questions and doubts Paul must assuage, and as long as both he and his supporters are most comfortable talking in terms of first principles, they'll be less than effective at convincing those who are not already true believers that Paul has what it takes to govern as president.