NASHVILLE, Tenn. – The Tennessee state senator said he was opposed to sex outside marriage, but his private life told a different story: He was having an affair with his 22-year-old intern.

When an extortion plot exposed married Republican Sen. Paul Stanley’s illicit relationship, he said he would be “clearing up” misimpressions later. He’s now clearing out his office, the latest politician caught in a sex scandal, this one made worse by not coming clean.

“If you can’t explain what you’ve done to your constituents in 30 seconds or less in a way they would accept, then don’t do it,” said Bruce Oppenheimer, a political science professor at Vanderbilt University.

“It’s amazing how many elected officials violate that very important conventional wisdom.”

As news of the affair broke last month, the 47-year-old Stanley dodged reporters and issued a statement calling himself a victim. The suburban Memphis lawmaker, a married father of two who taught Sunday school, said he wanted to set the record straight. But, he insisted, prosecutors had told him not to talk.

The details that emerged, however, did nothing to vindicate him. Court documents showed he had admitted the affair to investigators and acknowledged taking explicit photos of intern McKensie Morrison in his Nashville apartment. Prosecutors issued a statement saying he was not restricted from discussing the case. After a week of mounting pressure, he reluctantly resigned.

Even as he quit, he tried to blame Morrison, suggesting in a radio interview that the intern might face charges in the extortion case.

Her boyfriend, Joel Watts, is the only person charged in the matter, accused of trying to extort $10,000 from Stanley in April. Authorities have said they do not plan to file more charges.

Investigators say Watts demanded the money in exchange for not selling Stanley’s explicit photos of Morrison to the media. Morrison and Watts have said Stanley was the first to offer to pay.

Stanley kept constituents and colleagues — even the Republican speaker of the Senate — in the dark until the first court hearing in the case on July 20.

Tennessee Democratic operative Mark Brown, who blasted Republicans’ handling of the incident on his blog, said Stanley’s biggest mistake was appearing dishonest.

“First and foremost, tell the truth,” he said. “Crisis management does not mean that you alter facts. Tell the truth, and then shut up.”

Moments after submitting his resignation letter, Stanley went on a talk radio show in Memphis to say that his actions did not shake his moral ideals.

In nearly a decade in the Legislature, he repeatedly cited his belief in abstinence outside marriage as he opposed gay marriage, adoption by gay couples and family planning funding for Planned Parenthood.

“Whatever I stood for and advocated, I still believe to be true,” he said last week. “And just because I fell far short of what God’s standard was for me and my wife it doesn’t mean that that standard is reduced in the least bit.”

Voters were outraged, posting hundreds of comments on newspaper Web sites and writing letters to the editor.

“He wants others to stay out of his business while he jumps blindly into theirs,” Dot Truitt Walk of Memphis said in a letter to The Commercial Appeal. “All of those sanctimonious hypocrites should remember this.”

Though Stanley’s resignation is unhelpful to the GOP, it is not expected to affect his district’s solid Republican voting pattern. The GOP already controls the state Senate, though the governor is a Democrat. A special election will be held to fill Stanley’s seat.

Oppenheimer said the timing of the scandal may actually be better for Tennessee Republicans than if the affair had surfaced closer to the election.

“The Republicans are far better off that this happened in July 2009 than if it were July 2010,” he said.

Some Tennessee Republicans even made light of the situation. State Rep. Stacey Campfield of Knoxville wrote on his blog that another lawmaker told him the Stanley affair was “just more proof, Republicans are clearly irresistible to females.”

Other Republicans across the country have recently been caught in extramarital affairs, among them U.S. Sens. John Ensign of Nevada and David Vitter of Louisiana. Then there’s South Carolina Gov. Mark Sanford, who on his return from a secret visit to his mistress in Argentina confessed his affair at a tearful, rambling press conference.

But Tom Ingram, a longtime Republican consultant in Tennessee, said all public officials risk the same scorn if they advocate one set of standards while acting under others.

“Every public official espouses morality, just like every preacher does,” Ingram said. “And the higher standards you set for yourself and others, if you violate those along the way, you’re going to pay a higher price because you got caught in your own web.”