Paul would have gotten the "anybody but Obama vote" (95% of the republican party)
He would have gotten the anti-war independents
He would have gotten the anti-war/civil liberty democracts
He would have gotten A LOT of the young vote
Romney only got the first .
You can't prove the negative and I get your energy and slant, but if Romney couldn't beat Obama in this economy, I don't think Paul--whose policy initiatives are more stark--would have fared as well. The "anybody but Obama" group would likely have dwindled (or not shown up at the polls) with a Paul candidacy. A lot of those folks aren't anti-government in the same vein as Ron Paul. A lot of soccer moms in that group and while they don't cotton to a lot of the Obama agenda, they want (among other things) good schools, safe streets, and predictability. They have concerns over the size and scope of government, but my guess is Obama and company could have scared the living pants off a lot of these folks. The election was all about the economy and I just think Paul's solutions were too radical to give comfort to a populace that was very security-driven.
I doubt there are that many folks in any of the other groups you mention that would have appreciably put a dent in Obama's armor. The folks over at
The Nation despise Ron Paul and if there's a stronger contingent of anti-war/civil liberty Democrats anyplace other than there, I don't know where they'd be. I don't think the results would have exactly been Nixon/McGovern because the South is so solidly Republican now that most of those states would have gone Republican if a robot were the Republican candidate (Wait a minute. The Republicans did nominate a robot.), but I believe Obama would have won more comfortably. I can't prove that, but neither can you prove that Paul would have won or done better than Romney. It's one thing to have energy, but I've run campaigns and it takes more than a bunch of excited people bouncing around to win an election. Obama's ground game is simply phenomenal. It is well-funded, well-oiled, and extremely organized. There is very little wasted energy and the concern that those folks were going to sit it out due to Obama's first term was ill-founded.
All this said, I do believe that the movement devoted to Ron Paul (and the succession that will follow him, whomever that may be) will gain in strength. There was a great article in
Harper's a few months back and I agree there are a ton of young voters who are organizing through the Liberty Movement and that bloc will likely grow to be more influential. But it takes organization to win and in 2012, I don't think the organization was there.
In response to the "Iowa comment," Iowa, like a bunch of Midwestern states with strong populist roots, still has a caucus system to determine delegate allocation. Paul and Santorum did better in those states than in primary states because you need to have a motivated group willing to turn off the television (or skip Muffy's dance class or Biff's hockey practice) on a Tuesday night and head down to the local junior high school and sit for a couple of hours and talk about resolutions, issues, and candidates and figure out who to send up to the next level (legislative district, congressional district, or state) as delegates. Paul had this with his following and my guess is Santorum's followers hit the windshields with flyers in every Catholic church parking lot in caucus states to generate interest (and let's remember that Santorum won in Iowa, not Paul).
I think the Paul/Santorum dichotomy is going to be the issue Republicans have to resolve before 2016. While Paul and his followers are largely, but not exclusively, anti-abortion, they don't "wear" the issue in the same way that Santorum does and there is a considerable segment of the Republican party which is all about what they term "traditional family values." I think the younger generation of Paul-ites (Rand Paul, Rubio, Ted Cruz) try to keep a foot on both rails, but unless there's a workable fusion of those elements, I see the Republicans scuffling for a bit on the national level. Not to mention if a fusion of these two tribes becomes the base of the Republican Party, where does that leave the more standard fare featuring guys like Chris Christie?