The primary date will move to May 20, a period when more voters are around and engaged than the July elections of previous years. That could help boost more centrist candidates in the race and make it harder for some of the challengers Republicans are worrying about — especially Rep. Paul BrounPaul Collins BrounHundreds apply to fill Isakson's Senate seat in Georgia Joe Lieberman's son running for Senate in Georgia California lawmaker's chief of staff resigns after indictment MORE (R-Ga.) — to reach the primary runoff.

The move also gives whoever wins the GOP nomination a bit more time to prepare for the general election.

Georgia Republicans are nervous about who might emerge from their crowded primary field to face Democrat Michelle Nunn, a candidate many Democrats are excited about.