Former South Carolina Gov. Mark Sanford will try to overcome his next challenge on the road to political redemption today, as Republican voters in that state decide the winner of a closely watched primary runoff.

Sanford left office in 2009 as a national punchline after he invented a new euphemism — "hiking the Appalachian trail" — for cheating on his wife. Now, he faces former Charleston County councilor Curtis Bostic in a two-way race. Should Sanford win, he'd be just one step away from reclaiming the House seat he held for three terms in the late 1990s.

As voters head to the polls today, Sanford appears poised to do just that.

According to a survey released last week by Public Policy Polling, Sanford led Bostic 53 percent to 40 percent in a head-to-head contest. While primaries are tough to forecast because of their relatively unpredictable turnout, that margin was enough for PPP's Tom Jensen to label Sanford a "strong favorite" to win the runoff.

That finding came one week after Sanford topped 15 other candidates to win the first phase of the Republican primary with a robust 39 percent of the vote. Bostic placed a distant second with 13 percent, forcing the two into a runoff since no candidate received an outright majority.

There was some speculation after that contest that Bostic could consolidate support from the other candidates — six in ten voters had, after all, chosen someone other than Sanford. However, only one of the fourteen losing candidates has thrown his weight behind Bostic; six have backed Sanford.

Also aiding Sanford is the fact that his sex scandal, though it sent his approval rating tumbling and ended his governorship, is no longer quite so toxic. Sanford has gone on a mini apology tour as part of his campaign, asking voters in interviews and ad spots for their forgiveness. Plus, the issue hasn't been at the forefront of the primary race, with even Bostic avoiding it to instead focus on his fiscal bona fides.

Here's The Washington Post's Sean Sullivan:

Voters in the 1st District are very familiar with the matter, and it hasn't been a dominant focal point in the Bostic-Sanford back-and-forth.

The issue came up most prominently during a televised debate last week, only after the moderator raised it. Sanford admitted fault, and argued that the 2009 episode brought him humility that would serve him well on Capitol Hill. Without directly mentioning the matter, Bostic called Sanford a "compromised candidate." [Washington Post]

Adding to Bostic's woes, Sanford has clobbered him with a 15-1 fundraising edge, according to the National Journal. While Sanford has been free to spend heavily on ads, Bostic entered the second round of voting with only $56,000 in cash on hand, and had to loan his campaign an additional $50,000.

The winner of the runoff will go on to face Democrat Elizabeth Colbert Busch, comedian Stephen Colbert's sister, in a special election next month to determine who fills the House seat vacated when Sen. Tim Scott (R) was appointed to fill a vacancy in Congress' higher chamber. Polls have shown Sanford and Busch essentially tied in a hypothetical matchup, though those numbers may well change once the GOP primary is finally settled. A large number of respondents remained undecided in PPP's recent survey, and 77 percent of voters in South Carolina backed Mitt Romney last November.