CHARLESTON, S.C. -- Former South Carolina Gov. Mark Sanford can't seem to escape attacks on the extramarital affair that derailed his political career, which he hopes to revive in the special congressional election that is now a week away.

For months, his Democratic opponent, Elizabeth Colbert Busch, refused to criticize Sanford's affair -- which was uncovered when he visited his mistress in Argentina under the guise of hiking the Appalachian Trail. Sanford seldom found himself on the defensive, instead focusing on a message of redemption and seeking voters' forgiveness.

His opponent's campaign in recent days has been airing an ad blasting him for that lie, and Colbert Busch criticized him Monday for using taxpayer funds for some of those travels. The attacks came even as Sanford picked up the endorsement of U.S. Sen. Rand Paul, a tea party favorite who has said he is mulling a presidential run.

A new television ad from the House Majority PAC that went up on Wednesday tells voters not to cast their ballot for a man whose "betrayal of South Carolinians is more than a mile long."

A billboard erected on an interstate near Columbia -- outside the 1st Congressional District where Sanford is running -- brings further attention to his past, using Sanford's photo to advertise a website where people can meet partners for extramarital affairs.

Colbert Busch's campaign ad said she worked to provide trained workers for the Boeing plant in North Charleston and that Sanford knew it. The ad came after an earlier Sanford ad questioned her claim she "worked with Boeing."

"It's the same Mark Sanford who used tax dollars to visit his mistress in Argentina," the Colbert Busch ad says. "He disappeared for a week leaving no one in charge. He betrayed all who trusted in him and then lied to cover it up."

Sanford has benefited from name recognition in the mostly conservative district.

The ad from the House Majority PAC takes a similar tack. In it, a woman who claims she is a lifelong Republican says she could not vote for Sanford because "his betrayal of South Carolinians is more than a mile long."

"I used to be for Mark Sanford but not anymore. He skipped town to be with his mistress on Father's Day. Sanford even asked his wife for permission to have the affair and wasted our taxpayer dollars on himself. I'm a Republican, but Mark Sanford just does not share our values," says the woman, Jennifer Stark of Mount Pleasant.

Sanford held the same congressional seat for three terms in the 1990s, and has touted his conservative credentials as a budget-cutter.

Paul praised those credentials Tuesday in issuing his endorsement, saying that during his career, Sanford has been an advocate for limited government and cutting spending.

"Mark has proved during his time in office that watching out for the taxpayers and holding the line on spending are his top priorities," Paul said.

"I think in looking at my own record there's been a consistent theme of looking out for the taxpayers and the bottom line," Sanford said in thanking Paul for the endorsement. "Unfortunately, with respect to my opponent, it simply isn't believable she would be an independent voice given who has been funding her campaign."

Sanford has been hammering at Colbert Busch saying political out-of-state interests are funding her campaign. She has said she will be an independent voice answerable only to the people of the district.

Later Tuesday, Sanford and Colbert Busch both had campaign appearances before a Chamber of Commerce group and an NAACP chapter, although both were to give comments, not formally debate.

On Wednesday, Sanford will get a boost from his successor, fellow Republican Gov. Nikki Haley. She will make her first campaign appearance on behalf of her former mentor in Charleston to help raise money for Sanford during a fundraiser at a home on the city's famous Battery.

"Nikki believes it is critical that South Carolina speak with as much unity as possible on key federal issues facing our state, such as labor union powers, Obamacare, and deficit spending," said spokesman Tim Pearson. "Mark Sanford is clearly the candidate who will stand with our Congressional delegation in fighting Washington's overreach."

Colbert Busch -- the sister of comedian Stephen Colbert -- Sanford and Green Party candidate Eugene Platt are on the ballot May 7 in a special election to fill the vacant congressional seat vacated when Tim Scott was appointed to the U.S. Senate.