Sen. Johnny Isakson (R-Ga.), right, is retiring. (J. Scott Applewhite/AP)

Even before Sen Johnny Isakson (R) announced his retirement on Wednesday, citing his health, Georgia was one of those states where Democrats believe that they’re making inroads, fast.

If the stars aligned for them with the right candidate, they were hoping to take out Sen. David Perdue (R) next year on their path to win back the U.S. Senate majority.

Now, they could have a chance at two seats in Georgia. But winning either won’t be easy, and it looks as though they’ll have to do it without their star candidate in Georgia, Stacey Abrams, who reaffirmed Wednesday that she’s not interested in running for Senate.

Isakson is retiring at the end of the year, and Georgia law will set up an election for the seat in 2020. It’s still early to say who’s running, but a Democratic Senate operative called the news “interesting” and describe it as another “potentially competitive Senate race on the map this cycle.”

Democrats need to have a dream election to win the Senate majority. They need to pick up three seats and the White House, or four seats without the White House. They are looking very competitive in about three seats, but they also might lose as many as two or three seats.

Georgia is part of their equation, but only if they get the right candidates. This is a state President Trump won by five points, after all. So here’s what’s up with Georgia’s two Senate races.

The growing, diversifying Atlanta suburbs have helped make Georgia more competitive for Democrats. The state is “fundamentally competitive” based on its partisan makeup now, says one Democrat The Fix talked to. Even though she didn’t win, Abrams’s gubernatorial race revealed the partisan makeup of Georgia, shifting it slightly less red. In addition to winning a majority of younger and nonwhite voters, Abrams won a majority of women.

Meanwhile, Democrats picked up a congressional seat outside Atlanta, with Rep. Lucy McBath, and are trying to pick up more next year.

Democrats argue that even without Abrams running — it’s looking more and more as though she’s interested in a potential vice-presidential pick — they can make a statewide race in Georgia competitive.

While Abrams got 48.8 percent of the vote in her 2018 governor’s race, Democrat John Barrow got 48.7 percent of the vote in his attempt to be secretary of state. They are two very different candidates, but their similar voter profiles suggest that a number of Democrats not named Stacey Abrams can make Georgia competitive.

Former Georgia gubernatorial candidate Stacey Abrams said she will not be running for Senate. (Seth Wenig/AP)

Republicans point out that Democrats will need someone who can outperform even Abrams, who became a national star on the left and raised millions of dollars but still didn’t crack 50 percent.

Right now former Columbus mayor Teresa Tomlinson and Clarkston Mayor Ted Terry are running for Perdue’s Senate seat. Perdue is easily outraising both (which, of course, comes with being a sitting senator).

On Tuesday, 2018 lieutenant governor nominee Sarah Riggs Amico announced she was running for Perdue’s seat, but it came with news that a company she runs had filed for bankruptcy. (“It’s the reason I’m running,” she told the Atlanta Journal-Constitution.)

The news of Isakson’s retirement is still only hours old, and it’s not clear which other Democrats would run for the seat. The fact that the party doesn’t have someone waiting in the wings suggests its bench is shallow, Republicans say.

Then there’s the fact that Democrats are pinning their hopes for a majority in a state like Georgia in the first place — reflecting the uphill climb they have to win back the Senate next year. Winning the majority requires winning in states Trump won, such as Georgia or Texas, or keeping a Democrat elected in Alabama.

It’s worth pointing out that nonpartisan election analyst Nathan Gonzales argues that candidates aren’t the most accurate way to judge races a year out from the election. Maybe someone like Tomlinson will be a better candidate because she has no national profile — you just don’t know this far out, he wrote in May at Roll Call.

A the very least, we can say this with certainty: It’s unhelpful for Republicans to have to defend another seat when they are already on the defensive in seven of the 10 most competitive races this year.

What remains to be seen is how much defending Republicans will need to do in Georgia.