Just as telling was what was missing from the event. Cagle's speech had little of the base-pleasing red meat that's typical at Georgia Republican rallies - and that he has routinely used in past elections. He made no mention of Democrats and steered clear of any reference to his Republican rivals aside from saying he would avoid attacking his challengers.
"I am not going to be running a campaign that's going to tear someone else down," he said, adding that candidates who focus on attacks "don't have much."
That pledge will surely be put to the test over the next 18 or so months. Cagle might be the presumptive front-runner, but his entrance in the race hasn't cleared the field. Secretary of State Brian Kemp and state Sen. Hunter Hill are already in, and a half-dozen other GOP contenders are considering a run.
Cagle supporters are keeping a particularly close eye on two potential candidates.
The first is Former Rep. Jack Kingston, the Republican runner up in the 2014 U.S. Senate race and an avowed Trump loyalist. The second is Nick Ayers, the one-time Sonny Perdue aide and confidante of Vice President Mike Pence who could become a fundraising force. Both have signaled they are considering a run.
Democrats are gearing up for what could be a stiff challenge. House Minority Leader Stacey Abrams is widely expected to run, and several other Democrats are eyeing the race. They hope that Donald Trump's election will help rev up enthusiasm in next year's vote, much like it has transformed Georgia's 6th District race.
Cagle's campaign is already trying to strike what could be a precarious balance on Trump.
In an interview, he said he supports the president's agenda - but stressed his independence. And at his campaign kickoff speech, he avoided mention of Trump. Instead, he heaped praise on another Republican: Gov. Deal.
"I've been able to partner with him to make Georgia the No. 1 place in the nation to do business," he said.