Ron Paul is not really a Republican even though he is a registered Republican congressman from Texas but by standing on their side he gets access to the publicity from debates and other bonuses related to funding, etc.
He is a really libertarian and as such believes in a more isolationist role so that the US doesn't get involved in other countries affairs really and only candidate on this side who wants a complete pull out of Iraq now.
Ron Paul finished 3rd in 1988 Presidential campaign which was won by George Bush Sr.
He in many ways is a true conservative as really wants smaller government, limited taxes and believes the States should decide issues like abortion.
He wants the US to withdraw from UN and NATO as part of this not interfering in other countries view of the world.
Has a strong and passionate following who really desire him to run as a 3rd party candidate which he said he will not do.
He has a much more liberal view on drugs but does not support gun control.
It is safe to say he has no real chance of being elected by Republicans but is definitely a favorite on the Internet and the only really 3rd party potential candidate on either side (unless current NY mayor Michael Bloomberg decides to make a late run).
The only question with Ron Paul remains whether he will cave into pressure and run for President as a 3rd party candidate again.
He will definitely get plenty votes and maybe help to start a revolution where the 3rd party candidate one day becomes a viable, electable alternative for President.