In Georgia there is no official party registration to run for office. You can be a dues paying member of one party, and register to run as a candidate in the opposing party. It happens sometimes here in Gwinnett County. It is always funny to see copies of Party contibution reporting forms in campaign ads against that person. You can run for office without ever having been to a meeting or given a dime to that party. The primaries aren't conducted by the parties, but through district wide elections conducted by the state.
Dues paying members of any party can select a primary ballot for any party they choose (Hence, Cynthia McKenney whining about her race.) This is done because it is known that only one party has a chance of winning on election day. So, to get elected, you must "claim" to be from that party. This happens in both Republican and Democratic districts. In my county 85+ % of the primary ballots were for Republicans, but the general election split was closer to 60-40.
Look up the policital life of Vinson Wall. Gwinnett went Repub - so did he. After redistricting new candidates were always asked why Vinson wasn't running. These people didn't care what party he was in. All they knew was that he actually answered their letters and checked on their problems. The average voter isn't partisan - and if they have any general bias on that front, most would say that they vote for that party in charge, becasue their elected official will have power. In that case, the official is giving them excactly what they asked for!