In Iowa Romney Leads Among Republicans, Paul Among Non-Republicans

And that's why a Ron Paul win in Iowa will be basically meaningless.  From Rasmussen:

But Scott Rasmussen notes a significant difference between supporters of Romney and supporters of Paul. "Romney leads, with Gingrich in second, among those who consider themselves Republicans," Rasmussen writes. "Paul has a wide lead among non-Republicans who are likely to participate in the caucus."

The Paul Bearers will do their best to stack the caucuses with non-Republicans who are willing to caucus for Paul but will be unlikely to vote for him were he to become the nominee. This is a strategy designed to screw up the GOP nominating process and we can expect to see lots more of it in other states with open primaries.

The GOP should NEVER allow non-Republicans to vote in their primaries. NEVER. It's foolish to let the opposition pick your nominee.