"I think if the weather is pretty Tuesday and her most reliable demographic, 65 and older, comes out, Handel will be fine," said a Republican strategist working the Georgia Sixth District congressional race on election eve. "But if it's pouring down rain, she's in for a long night."

As it turns out, the forecast is for rain.

In the Atlanta-area district, Republicans who two weeks ago were cautious about guessing GOP candidate Karen Handel's chances to defeat Democrat Jon Ossoff are now even more cautious. Ossoff pulled out to a lead in the polls in the early days of June, but now the RealClearPolitics average of polls shows him up by just 1.5 percentage points, 49.3 percent to 47.8 percent.

Heavy early voting reflects intense interest in the race. In the April 18 primary, a total of 192,000 votes were cast. For this race, there were about 140,000 early votes cast in the period that closed Friday. Depending on who you ask, another 80,000 to 100,000 are expected on election day. So if the total number of votes is somewhere between 220,000 and 240,000 -- that's significantly more than that 192,000 last time around.

Where are those new voters going? Some Republican strategists involved in the race are looking at two critical measures. The first is Ossoff's edge in early voting -- no one doubts that he has won the early vote, but the margin will be critical. The second is how many Republican votes Ossoff will win. If the number creeps too high, Handel can't win.

On the early voting: "It's very simple," said an outside Republican strategist supporting Handel. "What does she lose early voting by? If Ossoff wins with 59 percent, that's bad. If he wins with 54 percent, that's good." That is, if Ossoff racks up 59 percent or more of the early voting, he'll have a lead so big that Handel can't make up the difference by winning the election day vote. If, on the other hand, Ossoff is at 54 percent or so, Handel could well surpass him on Tuesday.

In a WSB-Landmark Communications poll finished in the final days of early voting, Ossoff had 54.4 percent of the early vote, to Handel's 45.6 percent. That suggests a super-tight final result, but with perhaps enough room for Handel to squeak by. In another new poll of the early vote, the Trafalgar Group found Ossoff with just 51.3 percent of the early vote, to Handel's 48.7 percent. That's much better news for Handel. The problem is, no one knows which is correct, or whether either is correct.

The second factor, the Republican vote, is of deep concern to GOP strategists. "We've had some people who are Republicans and conservatives who are not motivated," said one GOP worker on the ground in Georgia. "There is a rumor that Ossoff is going to pick up 15 percent of Republican voters."

More than a rumor. The WSB-Landmark poll had Ossoff's support among Republicans at 15.3 percent. The Trafalgar Group poll had the number at 14 percent.

For Republicans, that is an excruciatingly close margin. "If Ossoff gets 15 percent of the Republican vote, he wins," said the outside Republican strategist. "If he gets less, he loses." And Handel wins.

In some ways, both sides are flying blind. Obviously President Trump is a factor, but so is the Democratic left and so is demographic change in the district. The way Republicans won the district in the past -- the seat was held by Tom Price, Johnny Isakson, and Newt Gingrich -- is not necessarily the way Republicans will win the district in the future.

For example, Handel has hit Ossoff continuously on the fact that Ossoff does not live in the district. (He lives a few miles away in Atlanta.) Handel points out her longtime residence in the Sixth, with the suggestion that Ossoff just can't be in touch with local issues the way she can.

But what about voters who are relatively new to the district? In the WSB-Landmark poll, nearly one-third of those surveyed were not living in the district ten years ago. Are they going to be bothered by where Ossoff lives? "Handel's last ad buy is still clinging to this idea that Ossoff is an outsider and she is one of us," notes a Georgia Republican. "But very few people in this district care that she went to elementary school here."

And then there is demographic change. According to U.S. Census 2015 estimates, there are 729,643 people in the Sixth District. Only 234,488 of them were born in Georgia; 327,448 were born in a different state, and 155,313 were born outside the United States. Plus, the numbers of minorities are growing: 96,154 Hispanics, 80,651 Asians.

So this is a different race from those in the past, and would be even if both sides weren't pouring $50-plus million into it. And that is what has left Republican strategists praying for sunshine in hopes that enough of their traditional voters can get to the polls. "This is the Wild West," said the strategist who was looking at the weather forecast. "You can't go look at your 3-ring binder and see how this is going to turn out."