(CNN) -- The last time Mark Sanford held public office, his political career was thought to be over after he admitted to an extramarital affair.
The South Carolina governor said he was looking for forgiveness when he began his bid for the congressional seat he held from 1995 to 2001.
On Tuesday, it appeared that his push for political redemption was working, as he took a 13 percentage point lead in a Republican primary runoff for the seat, according to early, unofficial reports from the South Carolina State Election Commission. His opponent, Charleston City Councilman Curtis Bostic, conceded to Sanford.
Whether to forgive him, the Republican told CNN in January, would be a personal decision for each voter.
"There's an amazing reservoir of human grace out there, there's a reservoir of God's grace that each of us have to access ourselves as best we can," he said during the interview on CNN's Piers Morgan Tonight.
Some voters, Sanford said, told him they will consider his background before deciding their vote.
"Forgiveness really is in the hands of the other, and I think it's incumbent upon each of us to make that decision for ourselves," he said, citing his 52 years in the state and two decades in politics.
Last month it appeared the political scales were once again tipping in Sanford's favor after he came in first in a 16-candidate primary. He finished with 37% of the vote, far short of the 50% needed to avoid a runoff, but he said that his first-place finish was "incredibly humbling."
Sanford, 52, had taken heat from his opponents in the crowded GOP primary field who criticized him for his past and for being a "career politician."
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, divorced in 2010, and Sanford finished his second term in January 2011.
The experience, he told CNN, changed his perspective.
"If you went through the level of destruction that I brought about it my own life, you have this yearning to construct something," he said in 2011. "We get our priorities mixed up in life. Fundamentally life is about relationships -- relationship to God and relationship to those around us."
He and his ex-wife, Jenny, were almost pitted against one another on the GOP primary ballot in March after both indicated their interest. But in January, Jenny Sanford said she would not seek the nomination, leaving Mark Sanford to formally announce his bid.
He is currently engaged to Maria Belen Chapur, the woman with whom he carried on the affair.
Chapur, who rarely appears in public with Sanford, was by his side during his victory speech.
The seat is up for a May 7 special election after Rep. Tim Scott resigned it upon his appointment to fill the U.S. Senate seat left vacant by Jim DeMint's resignation.
Sanford is expected to face a tough bid for the seat against Democrat Elizabeth Colbert Busch, the sister of TV political commentator Stephen Colbert.
And this time around, Sanford pitched himself as a fiscal conservative who spoke out on the issues of debt, deficit, and federal spending years ago, issues that are now very much at the forefront.
"We're having a new fiscal crisis, it seems, every couple months," he said. "So what I want to do is take what I've learned and hopefully apply it to again a great conundrum that now exists in Washington, which is how do we get our financial house in order."
CNN's Chelsea J. Carter, Catherine E. Shoichet, Jim Acosta, Paul Steinhauser, Kevin Liptak, Peter Hamby and Ashley Killough contributed to this report.