This week's painful confession of infidelity from South Carolina Gov. Mark Sanford was political theater. But it was also politics as usual: Nevada Sen. John Ensign, a Republican, admitted to having an extramarital affair last week.
And the recent U.S. political map of infidelity is bicoastal, bipartisan and bisexual.
Ensign and Sanford join a string of politicians who have admitted to infidelities while serving in office.
The list includes former North Carolina senator and former vice presidential candidate John Edwards, the Mayor of Los Angeles, Antonio Villaraigosa, former mayor of Detroit, Kwame Kilpatrick, Sen. David Vitter of Louisiana, former New York Gov. Eliot Spitzer and former Gov. Jim McGreevey of New Jersey.
Politicians know that sex scandal often spells disaster, insiders say, but it remains part of the political culture.
"I think some of these guys are wired in a way that they literally don't have the emotion of shame," Democratic strategist Neil Oxman said.
GOP strategist Chris Mottola said, "Elected officials have so much smoke blown at them and up them, they don't know right from wrong."
Edwards admitted as much in an interview last year with ABC New's Bob Woodruff.
"A self-focus, egotism, a narcissism that leads you to believe you can do whatever you want," he said. "You're invincible."
Psychologists say it's part of what makes them politicians.
"They have a set of traits that drives them into politics, that includes, risk taking, ability to handle uncertainty, being turned on by the adulation of the public," said Frank Farley, professor of educational psychology at Temple University in Philadelphia.
Even obvious hypocrisy is no match for some politicians. Sanford blasted President Bill Clinton during his impeachment scandal over the Monica Lewinsky scandal.
"What the American public cares about is the issues of integrity and the issue of trust," he said at the time.
There is, of course, another thing these politicians have in common. They are all men.
Testosterone at Work
"Testosterone is a powerful hormone," said Cokie Roberts, a veteran political observer and frequent contributor on "This Week with George Stephanopoulos.
"And it seems to drive some men to do things that they would not rationally do if they were thinking with another part of their bodies."