Paul is by far the best of the candidates when viewed from this side of the pond, though given the rest of the candidates that probably sounds more impressive a statement than it is. I cant believe he would ever win though, you would think that every mainstream media outlet would go nuts over it and Obama's fundraising would probably go up by an immense amount.
Actually, if Paul somehow miraculously made it through the GOP nomination process, he'd pull in a rather large plurality from both the Left and the Right.
A few of my lefty neighbors... to the point of being annoyingly so, who bought the ugly Honda Insight hybrid two years before the much cooler Prius came out, and had lefty political signs up in their yardall year round... yeah, those people. As popularity polls for Obama began to bottom out this past summer, these folks took down all their Democratic signs, and put up exactly two Ron Paul 2012 signs.
Libertarians on social issues, namely, do whatever the hell you want that doesn't hurt someone else, resonates well enough with many otherwise hard-left types, that they're willing to eschew Keynesian/Marxist economic policy and the welfare state to line up behind the man.
Or, maybe it's just drug legalization. I dunno.
The downside would be that Agricola is absolutely right, you'd see all sorts of crazy power shifts, and changes in PAC and individual donations and funding patterns shift to Obama. Especially a lot of traditionally conservative ones from the business, agricultural, manufacturing, and financial sectors. The common thread being they enjoy either profit, or protection from government largess.
Companies, groups, and lobby groups that may have a nominal Left/Right political predisposition, but more so have a heavily invested interest in the status quo. And for better or worse, Right or Left, anyone interested in the status quo above all else would scramble to prop up Obama.