Charleston, South Carolina (CNN) - Former Gov. Mark Sanford finished first in Tuesday's crowded Republican primary for the U.S. House special election in South Carolina, CNN projects. However, Sanford fell well short of the 50% margin needed to avoid a runoff.
The former governor will compete against Curtis Bostic, a former Charleston councilman, in a runoff election in two weeks. The third place finisher, state Sen. Larry Grooms, conceded the race Wednesday.
"Are you guys ready to change things in Washington, D.C.?" Sanford said to supporters at his campaign headquarters in Charleston on Tuesday night. All four of his sons attended the party.
"What we've earned is the honor of being on the playing field here for the next two weeks," he added, asking the crowd to redouble their campaign efforts. "Indeed, we are at that tipping point."
On the Democratic side, CNN projects Elizabeth Colbert Busch, sister of comedian Stephen Colbert, won the nomination.
"This is absolutely incredible. What a wonderful night," she told supporters at a victory party in Charleston, South Carolina. "It's the start of a new beginning, right?"
The longtime area businesswoman was considered the favorite on the Democratic side over opponent Ben Frasier. She'll compete against the Republican nominee in the general election in May.
The winner of the special election will fill the U.S. House seat vacated by now-Sen. Tim Scott, a Republican appointed to fill the Senate spot that Jim DeMint left last month.
"I am ready to go to Washington, D.C. to be your voice, so we're going to do that," Colbert Busch said.
The Republican primary ballot featured 16 candidates, including Sanford and Teddy Turner, son of CNN founder Ted Turner.
Sanford's re-entry into politics comes after an extramarital affair derailed his marriage and political career. As governor, he infamously told the public in 2009 he was hiking the Appalachian Trail while he was actually traveling to Argentina to carry on the affair.
He and his then-wife, Jenny, were divorced in 2010 and Sanford finished his second term in January 2011.
Sanford is asking the public for a second chance, and in his own informal poll of the voters, he said he's finding an openness to forgive, if not forget.
In an interview Tuesday night, Sanford said his first-place finish was "incredibly humbling."
"There's this amazing reservoir of human grace out there that's a reflection of God's grace, and I've seen it first hand," he said, adding that he looks forward to a "spirited contest" during the runoff.
Sanford's colorful not so distant past was far from the only distraction in the race.
Turner had family ties, deep pockets and a sudden rise in some internal polling. All that made him a big target.
Opponents filled mailboxes with attack ads on Turner, with some tying the candidate to one of his father's ex-wives, Jane Fonda.
"You know it's absolutely amazing how dirty the game is, how expensive the game is. It just doesn't make sense," Turner said.
John Avlon, a CNN political contributor whose family has lived in South Carolina for decades, said Sanford's honesty about his imperfect personal life has made him more relatable to voters.
"There is an affection for a guy who admits he's a sinner and asks for forgiveness, especially down here," Avlon said.
Despite his transgressions, the former governor insists he is worthy of the public trust. Sanford maintains he learned some important life lessons after wondering off-trail.
"Oddly enough, I think you learn from the valleys of life rather than the peaks," Sanford said.
CNN's Ashley Killough and Keating Holland contributed to this report.