Likely 2016 presidential candidate Sen. Rand Paul is a libertarian who's relatively dovish on foreign policy. According to Politico, this is giving big GOP donors pause. Katie Glueck reports that they worry "that a President Paul would dangerously scale back America’s activities abroad — a deepening concern in some corners as his star has risen within the broader party."

Former State Department official and Romney foreign policy adviser Brian Hook tells Politico: 

There is a Republican tradition, one could even say a bipartisan tradition, of American leadership in world affairs. Sen. Paul has placed himself squarely outside that tradition.

Lobbyist Ron Kaufman added, "The fact that he is, by self-definition, a libertarian, I think there’s concern among some of the donor class. …he's perceived as much more a libertarian on foreign policy and therefore more of an isolationist than, perhaps, a lot of donors feel." Kaufman added that he doesn't think Paul's views necessarily disqualify him, but they will make it harder to gin up donations from hawks. 

At the moment, Paul doesn't seem to concerned about his rep. Next week, he plans to do what he does best — filibuster a presidential nominee — to protest President Obama's drone policy

Paul's success will depend on a lot of things — how well the leading establishment candidate former Gov. Jeb Bush does, for one. A former Romney adviser and GOP donor tells Glueck, "For a lot of the establishment people that care about foreign policy, he has considerable concerns among that crowd. The interesting question is, how much does that crowd matter anymore? You still have … establishment people, a handful of people, who do care, whether it's Israel, Middle East policy, policy regarding China. But at the end of the day, if you look at primary voters, it's pretty low on their totem poll." 

In the meantime, Paul is personally calling Republican activists in Iowa to let them know he's serious about a run. He just doesn't think Iran is a nuclear threat