Sen. Lindsey GrahamLindsey Olin GrahamThe Hill's 12:30 Report — Sponsored by Delta Air Lines — GOP centrists in striking distance of immigration vote Dem leaders request bipartisan meeting on Russia probe Senate GOP urges Trump administration to work closely with Congress on NAFTA MORE's (R-S.C.) Democratic opponent has a white collar criminal past. 

Jay Stamper, Democrats' only candidate against Graham at this point, pled guilty to three felony charges associated with the illegal sale of securities in 2006. He agreed to pay back $5 million to more than 200 investors in 37 states and received fines and probation.

According to The State Stamper said that the charges resulting from the Washington state savings business he led were due to "a business mistake I made several years ago."

"I never meant to hurt anyone. There was no malice. … In a way I was reckless … but there were mitigating circumstances," Stamper said.

Stamper told The Hill the issue stemmed from a mistake on his lawyers' behalf.

"It was a business mistake, it was not intentional. I didn't intentionally break the law, and in addition to that I took extraordinary measures to make sure all the investors were made whole. In terms of reaching out to my own party, I've had a lot of positive response from Democrats. The party establishment has not always been completely supportive," said Stamper.

"Basically, I raised funds, my business did, on the internet under the advice of attorney, and using an exemption to federal securities laws, and apparently that exemption was not valid," Stamper continued. "Two sets of attorneys missed that as a result I was charged in Nevada for failing to register the securities and selling unregistered securities. I decided to plead guilty to that. I never lied to anyone, never stole from anyone, never cheated anyone and I took responsibility and I think people will take that into consideration. I've had a lot of good response from rank-and-file Democrats here."

Stamper isn't the first controversial candidate Democrats have put up for Senate in recent years. In 2010, unknown Alvin Greene (D), who at the time was facing criminal charges for allegedly showing an indecent photograph to an 18 year old, unexpectedly won the primary to face then-Sen. Jim DeMint (R-S.C.).

Graham is facing a handful of Tea Party challengers for his primary, but still looks to have the edge in that race. If he survives the primary, he's a virtual lock for reelection in the heavily Republican state.

--This story was corrected at 5:36 p.m.