A self-described "unapologetic conservative" whose campaign ran an eyebrow-raising ad that said he could use his own pickup truck to "round up criminal illegals," Kemp rode a national wave of voter contempt for the establishment in favor of bare-knuckled outsider politics.
He now faces Democrat Stacey Abrams, who could become the country's first black female governor, in a race that will test Democrats' assertion that changing demographics have turned the Republican stronghold into a swing state.
Kemp thanked supporters at a party in his hometown of Athens, Georgia, on Tuesday night and said he had won a "clear, convincing victory." He credited the White House's backing for sealing his win. "They poured gasoline in the fire and fueled the Kemp surge to victory," Kemp said.
Kemp portrayed the race against Abrams as a battle with the "radical left" as Georgia's future hangs in the balance. "Do you want a governor who is going to answer to Nancy Pelosi and Hillary Clinton?" he asked.
Abrams tweeted her reaction to Kemp's win Tuesday, saying "Tonight, I have an opponent: Kemp. The race for #GAGov may change, but our values never will. Service, faith & family guide our vision for GA: Affordable health care. Excellent public schools for every child. An economy that works for all."
"Stand with us," she wrote, followed by a link to a fundraising page.
Kemp beat once heavily-favored Lt. Gov. Casey Cagle, who outraised Kemp more than 2-to-1 and had a Rolodex of endorsements from establishment Republicans in the state including Gov. Nathan Deal.
In a tweeted endorsement last week, President Donald Trump pointed to Kemp's tough stance on illegal immigration and strong support for gun rights. With days left in the race, Vice President Mike Pence also stumped for Kemp on the campaign trail. Both reiterated their support for Kemp in tweets Tuesday.
Kemp's victory is likely to embolden Trump to become even more engaged in shaping the Republican Party in the final months of the primary season. And it is another election success for a Trump-approved candidate, following victories by Katie Arrington in South Carolina and Martha Roby in Alabama.
Nichole Jacobs went to Sandy Springs Christian Church to vote Tuesday for Kemp, citing his stance on immigration. Jacobs sends both her children to private schools, and feels her affluent Atlanta suburb is overrun with "illegal immigration."
"People are moving out of Sandy Springs to get into a better school district or putting their kids in private schools," Jacobs said.
Cagle began to lose ground after the release of a secret recording in June in which he says he helped pass a "bad public-policy" bill for political gain. The recording was made without Cagle's knowledge during a private conversation with former GOP gubernatorial rival Clay Tippins, who last week endorsed Kemp.
"Trump is a very powerful man," Cagle told watch party attendees Tuesday night in Atlanta after conceding to Kemp. He pumped his fist in the air, saying he put his best foot forward in the race as he congratulated Kemp.
"We have to rally behind him, so he can before the next governor of the state of Georgia," Cagle said of Kemp. "He is a person who is undeniably ready to lead this state. We have to rally behind him."
But Keenan Rogers, a 25-year-old Cagle supporter, was not yet convinced. He said he is leaning toward voting for Abrams over Kemp, but hasn't come to a decision yet.
"My knee-jerk reaction is to vote for Stacey Abrams," Rogers said, but added that he wanted to do more research on both candidates. "She might be a step forward for millennials ... But right now, I'm a little apprehensive."
Kemp had received widespread criticism — and national headlines — with television ads in which he pretends to intimidate a young man interested in his daughter with a shotgun and says he has a big pickup truck "just in case I need to round up criminal illegals and take 'em home myself."
Kemp's opponents also hammered his record of securing voter data as secretary of state, in a line of attack likely to become a refrain for Abrams during the general election.
Cagle labeled Kemp "inKempetent," pointing to a 2015 incident in which Kemp's office inadvertently released Social Security numbers and other identifying information of millions of Georgia voters on disks sent to members of the media and political parties.
Kemp said a member of his staff was responsible for the error, that person was fired, and procedures were changed.
Kemp's office made headlines again last year after security experts disclosed a gaping security hole that wasn't fixed until six months after it was first reported to election authorities. Personal data was again exposed for Georgia's 6.7 million voters, as were passwords used by county officials to access files.
Kemp spokeswoman Candice Broce laid the blame squarely on Kennesaw State University, which had a contract to manage the system. "It was not our system. It was not our equipment. It was not our network," Broce said.
In the race ahead, Democrats point to a Georgia electorate that has become more urban and less white in recent decades as a sign they may be able to break the GOP winning streak for statewide office. Abrams already has star power, having garnered national attention when she won more than 76 percent of Democratic votes in her May 22 primary.