And then 2015 happened. Paul announced his campaign in April, and he held steady near the front of the pack for a bit. Over time, though, his support drifted away.
Paul's focus on individual liberties seemed like a natural fit for the electorate in New Hampshire. Even there, though, voters looked elsewhere.
It's impossible not to contrast that with his father's performance in the last two cycles. Ron Paul earned 35 delegates in 2008 largely on the strength of his performance in a number of western and rural states. In 2012, Paul earned 101 delegates -- enough to cause problems at the convention.
That year, Ron Paul's support was steady. He saw a slight increase as voting began, but generally hovered around 10 percent in national polls.
And in Iowa, he very nearly won the state, finishing a close third behind Rick Santorum and Mitt Romney.
Why? Ron Paul had a strong base of supporters that were with him at the beginning and who responded well to his consistent, focused, limited message. Young Republicans embraced him the way young Democrats are today embracing Bernie Sanders. (To Paul's disadvantage, there are more young voters on the left than on the right.)
Rand Paul's campaign was different. It was more traditional, with traditional events and, in some cases, a more traditional willingness to be flexible on issues. As our Chris Cillizza noted, his non-interventionism became a liability in a Republican electorate that is increasingly concerned about foreign policy and the threat of terrorism, given the spread of the Islamic State. His position as the rebel throwing bombs at Washington was usurped entirely by the rise of Ted Cruz, Ben Carson and, of course, Donald Trump.
Paul didn't have the coalition or the political moment that his father did. The younger Paul peaked way, way too early. He peaked before his campaign even began.