The moves come three weeks before a special election to replace former Republican Rep. Tom Price, who Trump tapped as secretary of Health and Human Services.
The National Republican Congressional Committee -- the House GOP's campaign arm -- is launching cable television, radio and digital ads and is placing five field staffers into the district next week, according to a GOP operative familiar with the efforts.
The Republican National Committee, meanwhile, already has six staffers on the ground, and plans to increase that to 15 before the April 18 contest, the Republican operative said. The RNC has opened one field office in the district and soon plans to open a second.
The efforts are all geared toward increasing Republican turnout -- rather than supporting any one of the 11 GOP candidates in the 18-person field.
It comes ahead of a jungle primary: All 18 candidates will be on the ballot April 18. If one tops 50% of the vote, that candidate is the winner. But if none do, the top two finishers will advance to a June 20 runoff.
The 30-year-old Ossoff -- a former staffer for Rep. Hank Johnson and a documentary filmmaker -- has consolidated Democratic support and is buoyed by an active regional anti-Trump grassroots effort, and has more than $4 million in the bank thanks in part to the endorsement of the liberal blog Daily Kos.
That's left Republicans fretting about whether an enthusiasm gap between the parties could allow Ossoff to eclipse 50% in the jungle primary.
The NRCC's independent expenditure arm, which cannot coordinate with the committee, is also expected to spend on TV ads. And the Congressional Leadership Fund super PAC is already spending $2.2 million on ads attacking Ossoff.
Stoking GOP fears is the district's big swing left in the 2016 presidential election.
The district, which favored Mitt Romney over President Barack Obama by 23 points in 2012, went for Trump over Hillary Clinton by just 2 points in 2016. Reliably red Cobb County backed Clinton, the first time it had supported a Democratic presidential candidate since former Georgia governor Jimmy Carter was on the ballot.
Georgia's 6th District is wealthier and more highly educated than the Atlanta area and the state overall. It also includes relatively large numbers of Hispanic, Asian and foreign-born residents.
Democrats hope the special election will be a positive omen for similar contests in the 2018 midterms in places like the Texas suburbs, Orange County, California, and near Minneapolis, Minnesota.
The special election is one of four to replace House Republicans who Trump tapped for Cabinet posts -- and is the most likely to change hands. Democrats also hope to compete in a Montana race to replace former Rep. Ryan Zinke, now Trump's Interior secretary.