Runoff day is finally here, kids. First, check out our premium story on why the Republicans never want this nine-week slog again. This evening, monitor the election returns at ajc.com and follow us on Twitter.

For an in-depth look at the candidates, read our profiles of Rep. Jack Kingston and businessman David Perdue. And throughout the day, keep tabs on these five things we'll be watching as Republicans decide which one of the candidates will be their U.S. Senate nominee.

1. Overall turnout: Will the rain and the negativity of the race depress turnout that was already dismal in the May primary? We also encountered plenty of folks who still were not used to a July runoff, so voter confusion is at play too. If turnout is lower than 10 percent, the likely beneficiary is Kingston -- who has the Republican clubs and county sheriffs and small-town mayors working their networks on his behalf.

Secretary of State Brian Kemp, whose office oversees elections, won't venture an estimate. Still, he said, it's hard for too many voters to claim ignorance with the TV barrage and direct mail out there.

2. Who's making inroads in metro Atlanta? Former Secretary of State Karen Handel of Roswell and Rep. Phil Gingrey of Marietta endorsed Kingston and have been hitting the trail for him. If Handel, in particular, can swing her metro Atlanta base Kingston's way it could prove decisive. Perdue's camp, in turn, unleashed former Gov. Sonny Perdue, his first cousin, on the metro Atlanta market on Monday in making a closing argument for the gig.

3. Can Kingston run up the score in the southeast again? Kingston won a whopping 75 percent of the vote in his congressional district in the primary and got strong turnout there. A runoff in the 1st  District should help him, but early voting there was down compared with the weeks before the primary. And a pro-Perdue Super PAC was on air in Savannah with the aim of driving up Kingston's negatives - and keeping home Savannah residents who have rarely heard an attack on their congressman.

4. Will Perdue's outside-ATL focus work? An analysis of ad spending obtained by the AJC showed some striking numbers for the nine-week runoff: Kingston and his allies spent $3.02 million on TV ads, while Perdue and accompanying PACs spent $2.22 million. But the distribution is uneven.

Kingston & co. outspent Perdue & co. by nearly $1 million in the Atlanta market, but Perdue forces had a $90,000 edge in Macon, a $50,000 edge in Augusta, a nearly $30,000 lead in Savannah, a $10,000 lead in Albany and a $15,000 lead in Columbus. We'll be interested to see if votes in those markets favor Perdue accordingly.

5. How late will we go? Yes there will be fewer votes to count, but Fulton and DeKalb counties tend to come in late, and Savannah's Chatham County could play an out-sized role thanks to Kingston's roots. This one could be a squeaker. Who needs sleep, anyways?