Make or Break: Presidential candidates are a breed apart, often propelled by traits that have shaped their careers and have deep roots in their personal histories. In the coming weeks, The Post will explore a key characteristic for each of the leading contenders that could help make him or her the country’s next commander in chief -- or sink their presidential ambitions.

The Pauls are the other political dynasty in presidential politics, and if they’re not quite the Bushes or Clintons, they’re still a recognizable brand, one crackling with intensity and quirky appeal.

Rand Paul’s ability to sell himself as the most libertarian of the presidential candidates — defending civil liberties at home and opposing military adventurism and nation-building abroad — is what can set him apart from his rivals. But those unconventional ideas could also box him in. Libertarians don’t win national elections, unless you count Thomas Jefferson in 1800 and 1804.

Still, Rand Paul’s greatest asset is the ideological jet fuel that helped his father get more than 2 million votes in the last set of Republican primaries. The son wants to convert that stuff to something less volatile and explosive. In his hands, it’s ideological kerosene.

Rand Paul is a more nimble, less predictable, more pragmatic politician than his father, who said “nay” so often in Congress that he was known as “Dr. No.” The younger Paul is an ophthalmologist who has won just one primary and general election and is still growing into his identity as a politician. But it’s clear he has been shifting closer to mainstream Republican positions, particularly on national defense, going so far as to call for a bigger Pentagon budget.

He’s even hedged on the “libertarian” label. In a recent tweet he wrote: “I’m a constitutional conservative. Libertarianish. Have a foot in both camps.”

This is an aspiring commander in chief walking a very fine line.