COLUMBIA, S.C. (AP) — South Carolina political strategist Richard Quinn has boasted a client list that includes Republican notables such as Lindsey Graham and John McCain. The veteran consultant's name has long been synonymous with Republican political success in South Carolina.

Quinn's indictment this week on criminal conspiracy and illegal lobbying charges could mean difficult and, at the very least, awkward circumstances for the remaining Republicans who still rely on him for advice. Not to mention the vacuum it could create if Quinn — who's advised presidential hopefuls in this early voting state for nearly 40 years — sits out the next White House cycle.

Quinn, 73, began his consulting business in South Carolina in 1978, when the now deep red state was dominated by Democrats. Helping flip control to the GOP, Quinn began advising legions of Republicans within state politics, including his son, state Rep. Rick Quinn. Now, both Quinns are under State Grand Jury indictment, as are a pair of other Quinn clients. Two more - the state's former House speaker and former majority leader - have already pleaded guilty to misconduct.

Quinn's been influential in presidential primaries here since 1980, his shop becoming the first stop for Republicans seeking to make a mark in the state's first-in-the-South primary. For more than 30 years, the state's primary winner went on to become the GOP nominee, a streak Quinn helped start in 1980, when he was hired by Ronald Reagan.

Quinn started a long relationship with John McCain in 2000, forging a bond despite the Arizona Republican's primary loss to George W. Bush. The two would team up again eight years later, with Quinn's firm propelling McCain to South Carolina victory and the Republican nomination.

Quinn has been advising Lindsey Graham since 1994, when the political newcomer became the first Republican to represent South Carolina's 3rd District in more than 100 years. When longtime Quinn client Strom Thurmond retired from the U.S. Senate, Quinn shepherded Graham's 2002 bid to replace him and has worked with Graham in every election since. When Graham ran for president last year, Quinn was in his corner.

Since 2002, Graham's campaigns have paid Quinn's firms nearly $3 million. Earlier this year, Graham said he would wait and see where the investigation went, calling Quinn "a friend for a very long time." It's unknown what role, if any, Quinn plays now with Graham.

Quinn has also advised U.S. Rep. Joe Wilson and his son, South Carolina Attorney General Alan Wilson. While investigating state House Speaker Bobby Harrell, the first lawmaker charged in what has become a yearslong investigation, the attorney general transferred the case to a special prosecutor, citing an unidentified conflict. Joe Wilson's campaign says it no longer retains Quinn for consulting and has no plans to use his services in next year's election.

Quinn's lawyers haven't returned messages seeking comment. The indictments give few details, but accuse him of trying to influence state lawmakers' votes on unspecified issues without being a registered lobbyist. Prosecutors also say Quinn conspired for more than a decade with other lawmakers, including his son, to skirt ethics and campaign finance laws for personal profit.

For now, his remaining clients wait and see what becomes of this powerful political player.

"I think the indictments make him radioactive with anybody looking to hire a political consultant," said Dick Harpootlian, a Columbia attorney and former chairman of the state Democratic Party.

Harpootlian said he regarded Quinn as a worthy adversary during their time in politics. But the former prosecutor also said his experience trying public corruption cases gives him an idea of the challenges Quinn is facing.

"I'm disappointed to see him in this spot," Harpootlian said. "When you're playing in the public sector ... there's a standard - lines you can't cross. We'll wait to see if he crossed them or not, but I think as a political consultant he's going to have a tough time going forward."

Joel Sawyer, who served as Gov. Mark Sanford's communications director and executive director of the state GOP, said, for politicians, the indictments mean working with the Quinns could now become a liability, instead of an asset, to their brands.

"Whether the charges stick or not, it's hard to think of anyone else whose entanglement in a probe of this nature would create an influence vacuum like this," Sawyer said.

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Kinnard can be reached at http://twitter.com/MegKinnardAP . Read more of her work at https://apnews.com/search/meg%20kinnard