Ron Paul is a member of the Republican Liberty Caucus, which is the "Libertarian wing" of the Republican Party; much like the Progressives are the Socialist wing of the Democratic Party. And that's how they got their start (running as Ds).
What Ron Paul is doing makes perfect sense and is totally legit, if you ask me.
However, getting back to the 1st paragraph, the Libertarian wing is only trying to get the GOP back to its original conservative values, whereas the Progressives are leading the Democratic party further left, where they have never been before.
One is a traditional move, and the other is, well, a progressive move.