The Republican primary campaign to succeed Mr. Sanford featured two operatives claiming to have had extramarital affairs with Ms. Haley (who strenuously denied the accusations) as well as a Republican state senator dismissing her with an ethnic slur.

Image Alvin Greene is the Democratic nominee for the Senate seat currently held by Jim DeMint, a Republican. Credit... Mary Ann Chastain/Associated Press

Now comes Mr. Greene, adding Democratic balance to the state’s Republican-dominated scandal sheets of recent vintage. Mr. Clyburn immediately called for someone to investigate Mr. Greene’s candidacy  who paid for the campaign, who was behind it, how did he ever win?

Mr. Harpootlian, a former district attorney, wants to know why Mr. Greene had not filed any papers with the Federal Election Commission, and Don Fowler, a former Democratic National Committee chairman from South Carolina, said he suspected that someone tampered with the voting machines.

“There is something genuinely mysterious about this whole thing,” said Mr. Fowler, whose wife, Carol, the current chairwoman of the state’s Democratic Party, has called for Mr. Greene to step aside.

Mr. Greene said he had no intention of doing so. He said the whole gambit has been his idea, that he paid the entry fee and that his was  and remains  “a self-managed campaign.” He said he would challenge his Republican opponent, Senator Jim DeMint, to a debate in September. “It will be one hour. Live. On a major network,” he proposed.

Mr. Greene said he was determined to go through with this, which would seem to belie the somewhat shell-shocked demeanor he has projected in several interviews over the last 72 hours. “Can I end this?” Mr. Greene asked in the middle of a brief interview with a local television station in front of his house Wednesday. It might as well be his campaign’s official motto, or wish, at least as far as leading Democrats are concerned.

“Sad,” Mr. Clyburn said, referring to the spectacle that Mr. Greene has become on the cable and YouTube circuits.