When Democrats flipped Georgia in 2020, Bishop Reginald T. Jackson, the leader of the African Methodist Episcopal Church’s Sixth Episcopal District, had been in the state just four years.

That was all the time he needed to turn a disjointed operation into a political machine. His success in mobilizing Black voters of faith played a key role in sending Joseph R. Biden Jr. to the White House — and two Democrats, Raphael Warnock and Jon Ossoff, to the Senate.

Now, Bishop Jackson, who is based in Atlanta, is leaving the state he helped make competitive. He will preside over the Second Episcopal District, which includes churches in North Carolina, Virginia, Maryland and the District of Columbia.

His departure, in keeping with rules that dictate a bishop may remain in a district for only two consecutive four-year terms, creates a critical leadership void in the organizing infrastructure that Democrats are relying on to turn out the vote for Vice President Kamala Harris just months before the election. Moreover, it could pose new challenges for the state’s network of activists and operatives already facing significant hurdles to replicating their past successes.

“Bishop Jackson enabled us,” said Rev. Timothy McDonald, the senior pastor of First Iconium Baptist Church in Atlanta. He credited Bishop Jackson for taking their work “beyond an idea — which preachers have a lot of — to an actual plan of how we’re going to turn out the vote.”

The bishop, 70, is leaving as Georgia re-emerges as one of the most prominent swing states in the presidential election. Ms. Harris and her running mate, Gov. Tim Walz of Minnesota, are kicking off a bus tour through southeast Georgia on Wednesday that will culminate in Savannah, sending a clear message that Democrats believe the state is back in play after former President Donald J. Trump built up a double-digit polling lead against President Biden.