I have thought about this, and wouldn't Ron Paul probably pull more away from the democrat candidate then the republican? Assuming Hillary wins, Ron Paul is the only legitimate antiwar vote and thus many young people and far left would be a fan (they would also be bigger fans of his libertarian views on social issues as they relate to government interference). I don't think a republican gets hurt by adding another antiwar candidate.
The far left are not fans of libertarianism. Libertarians oppose welfare, gun control, affirmative action, and federal funding of the arts - all liberal sacred cows.
You give the far left too much credit.