Tuesday will put a temporary end to our biennial debate over whether Georgia remains a reliably red state, or whether we are finally shifting – as changing demographics insist that we must — toward the bluish end of the spectrum.

But in a way, this has already happened. At least in a very large portion of the state.

Four years ago, in the 28 counties that the U.S. Census Bureau defined as the greater metro Atlanta area, President Barack Obama edged out Republican challenger Mitt Romney by a mere 12,577 votes out of 2.2 million cast.

Residents of those counties, a footprint that extends from Bartow in the north to Pike in the south, made up 57 percent of the 2012 electorate in Georgia. Romney walked away with Georgia’s 16 electoral votes only because he was able to run up the score in the state’s other 131 counties, winning 59 percent.

The same dynamics apply this year. Except that the blue of greater metro Atlanta is likely to be a shade deeper. In that sense, Tuesday isn’t just about the race for the White House or U.S. Senate. It’s about which metro Atlanta counties will flip from the Republican column to the Democratic one.

Many eyes are on Gwinnett County and its changing face. For the first time, whites no longer make up a majority on its voter registration list.

But a better bet is on the other side of metro Atlanta: Henry County, home to a stunning shift in population.

Over the last 10 years, the number of white voters in Henry County has decreased by nearly 4,000. The number of registered African-American voters has increased by 23,728 – more than 200 percent.

“I know Republicans see it coming, if not this election, the next election,” said Richard Ray, the retired president of the Georgia AFL-CIO and a 17-year resident of Henry County.

In 2014, Jason Carter became the first Democratic candidate for governor to win Henry County since Zell Miller did it in 1990.

Democrats are guaranteed their first county-wide position in years on Tuesday. In Henry County’s race for district attorney, the GOP challenger withdrew in September, leaving Democrat Darius Patillo as the only candidate.

Democrats are also threatening the state House seat now held by Brian Strickland, a Republican from McDonough. The Democrat is newcomer Darryl Payton.

But most interesting may be the race for chairman of the Henry County Commission. Incumbent Tommy Smith, a Republican, is bowing out. Republican June Wood and Democrat Carlotta Harrell are both African-American.

Harrell ran for commission chairman in 2012. In defeat, she won 47 percent of the vote. The black vote in Henry County has increased by nearly 4,000 since then. Whites were 51 percent of Henry’s voting population four years ago. Today they are 46 percent.

Henry County Republicans have adapted. They are attempting to shed the racial identity that is such a strong element of Georgia politics.

“Republicans chose [Wood] over two white candidates,” noted Mark Rountree, a GOP pollster who does quite a bit of work in suburbia – and is a strong advocate for increased diversity within the GOP. “Obviously, the county is changing a lot, but the Republicans there are doing what they need to do to remain competitive,” he said.

Rountree notes that the way Henry County has exploded with growth offers Republicans a path for survival. “These are people that are moving there, and they’re buying houses. They’re private property owners. It may be very well that they’re more conservative than in other areas,” he said.

There are Democrats who agree with Rountree – to a point. “You see the BMWs, and Mercedes and that sort of thing,” said Ray, the union veteran.

State Rep. Stacey Abrams of Atlanta runs the state House Democratic caucus that is pouring resources into the District 111 race.

“You have as much appetite for black suburban living as you do for white suburban living. Henry County, over the last decade, was a low-cost, high lifestyle suburban area,” Abrams said.

“I see it as the 21st-century version of DeKalb County. If you think of how DeKalb County began as a bedroom community for Atlanta, I think Henry County has become a similar iteration of that.”

Both Rountree and Abrams agree that the binary nature of Henry County’s new politics – black vs. white – makes it an easier target for Democratic gains than other counties. Like Gwinnett, which hasn’t been carried by a Democratic presidential candidate since Jimmy Carter in 1976.

Ten years ago, whites made up more than 68 percent of Gwinnett’s voting population. Now, they’re 48.5 percent. African-Americans are 27 percent. Asians and Hispanics each now share 6 percent of the county’s voter registration list.

You’re not just dealing with different communities in Gwinnett, but different cultures.

“If you look at Henry County, it’s strongly driven by African-American growth. Gwinnett County is driven by almost equally by Latino, Asian and African-American growth,” Abrams said. “Which means that your opportunity to build coalitions is different.”

Donald Trump aside, African-Americans, Asians and Hispanics aren’t necessarily natural or permanent allies – a fact that Republicans, if they’re smart, might take more notice of. “It’s a very different Rubik’s Cube,” Rountree said. “It’s dealing with other languages, even.”

Speaking of which. Last month, Secretary of State Brian Kemp, a Republican who might harbor gubernatorial ambitions, unveiled new video tutorials on voting, placed on his government website — in Hindi, Korean, Mandarin Chinese, Spanish, and Vietnamese. As well as English.

Certain English-only advocates within the Georgia GOP immediately condemned the secretary of state. But others quietly applauded Kemp’s effort.

For Republicans, the loss of smallish Henry County next Tuesday would be painful, but tolerable. The fight over a behemoth like Gwinnett is likely to be a much longer game, with control of the state Capitol at stake.

If Republicans are to keep it, new friends are required.