Haley vaulted from unknown state legislator to national figure overnight with the endorsement of Sarah Palin, the former Alaska governor and 2008 GOP vice presidential nominee.
Palin's appearance on the Statehouse steps cemented the tea party following Haley had quietly been building.
Haley, as a protégé of Gov. Mark Sanford, picked up much of Sanford's support without being dragged down by the extramarital affair that crippled him. She was accused of two affairs of her own by two different men.
Then there is the discussion about her conversion in her mid-20s to Christianity, though she acknowledges continuing to occasionally visit a Sikh temple when her family is in town.
"Her candidacy demonstrates how much progress the South has made," said Atlanta political strategist Bill Crane, who is not advising any races this year in the Palmetto State.
Barrett, a Republican stalwart, hasn't had much success trying to slow Haley's momentum. Crane attributes that to the challenges of a man attacking a female opponent.
"You can't carry the paper bag with the gross stuff in it without some of it getting on you," he said.
The unsubstantiated allegations might have made Haley stronger, according to Bruce Ransom, a political science professor at Clemson University.
"During that period of the charges, she not only was able to maintain the lead that she had gotten from former-Gov. Palin's appearance but some polls showed that she might have added to it," he said.
In a year when voters are furious at incumbents and those too closely associated with tax-and-spend policies, Haley has aligned herself with the tea party movement and other conservative groups.
The winner of the runoff will face Democrat Vincent Sheheen, a state senator from Camden.
Haley defeated Barrett 49 percent to 22 percent statewide, but in Aiken County, results from the June 8 primary show Barrett garnering nearly 34 percent of the vote. Haley received about the same percentage in Aiken County as she did statewide, coming up about 1 percent short of becoming the nominee.
The other candidates, Attorney General Henry McMaster and Lt. Gov. Andre Bauer, collected a much smaller percentage of the vote in Aiken County than they did statewide.
Twenty-four Republican races are heading to a runoff Tuesday. There are just seven Democratic runoffs, which largely involve county positions. There are no local runoffs for either party in Aiken County.
Ransom said he doesn't expect Haley to provide any coattails to other candidates in the runoff, but her growing popularity could boost turnout.