For years, many conservatives have agitated for closed primaries, based on the simple principle that Republicans should choose the Republican nominee, and Democrats should choose the Democrat nominee.
And as long as conservatives have made that argument, lunkhead establishment types have made the claim that in closed primaries, might chose a true believer, a person who had no cross-over appeal. By having Democrats and independents participate in Republican primaries, we would be more likely to pick somebody who would be palatable to undecided voters.
To those who despise closed primaries, I give you Iowa, and Ron Paul.
Game. Set. Match.