Remember that SC is a open primary. The Democrats and Independents will vote enmasse for Paul, giving him the appearance of more support than he has. That will encourage him, and he doesn’t need much, to run as a third party Independent and syphon some votes from the Republicans.
Democrats are voting for Romney not Paul. Every democrat I know thinks Paul is nuts. He cuts into thier entitlements and is anti-union. They don’t mind Romney, even if he wins the general election they would be happy since he pretty much R’obama’ny.