And then there is the State of Virginia -

The Republican Party of Virginia will require all citizens of the state voting in the Republican primary on March 6, 2012 to sign a loyalty oath before being permitted to cast their votes.
Put plainly, anyone who shows up at the polling place must sign a form wherein he or she swears to support the Republican candidate who wins the nomination. Refusal to sign the pledge results in revocation of the right to vote in the Republican primary election.
source



I have a son in Virginia. He said he will not vote in the primary if this is in effect.