Teacher Lee Benedict filed to take on Mr. Harbin. Mr. Benedict has been critical of several delays Mr. Harbin has received -- some at the request of prosecutors -- in a 2007 DUI case that has yet to go to court.
Mr. Benedict got less than 4 percent last year in a special election to fill the term of Jim Whitehead, who resigned to run for Congress. Mr. Benedict came in fourth behind winner Bill Jackson and another Republican and also behind a Democrat.
That kind of intraparty race, or any kind of challenge at all, is unusual this year for incumbents, according to an analysis of the online records maintained by the Secretary of State.
If elections for the General Assembly were to be held after Thursday's fourth day of qualifying, almost three-quarters of House incumbents filing for re-election wouldn't have to lift a finger.
Almost nine in 10 wouldn't need to concern themselves with a challenger from their own party.
In all, 73.3 percent of House members who have qualified to run for another term face no opponent to this point, and 86.7 percent are unopposed in their district for their parties' primary election. The advantage, so far, is cutting toward the majority GOP: If races where incumbents haven't filed are included, 83 districts in the House would go to Republicans without a general election fight and 67 would go to Democrats, leaving the GOP with eight seats to win in contested elections to maintain their majority.
The numbers are slightly lower in the Senate, where 62.2 percent of members face no opposition, with 79.2 percent having no reason to fear a primary foe. There, the GOP holds a 26-20 edge.
Republicans saw the numbers as a sign that their party's leadership is well-received.
"I think it signifies that the Georgia Republican Party, over the last several years, had done a good job of recruiting to run and electing good, quality candidates to the Legislature," said Ben Fry, the GOP's executive director.
Democrats, unsurprisingly, saw things differently.
"I think it's a mark of districts being drawn on partisan lines," said Martin Matheny, the party spokesman.