Infidelity is definitely mainstream behavior, and I can give anecdotal evidence of that firsthand.
In the early Eighties, older Baby Boomers who had married young began having affairs with coworkers. There was a new openness about this that I found disturbing. Married men were taking their mistresses out to parties and openly introducing these women as their girlfriends. The women had no shame about it, no doubt believing that the man would honor his promise to leave the wife who "didn't understand" him. (It didn't occur to them that they were merely inheriting men who cheated on their wives.)
I saw people and families destroyed by this behavior, and while it slowed down as the Eighties progressed, men of power, always seen as sexually attractive by women, continued to act this way.
Keep in mind that long before Monica showed up, there were rumors that Clinton had been a horndog in Arkansas, was still a horndog as president, and was partial to oral sex. Bill Maher on ABC's "Politically Incorrect" make a joke right after Clinton's 1996 re-election about Clinton being so confident now that he had started dating again. People pretty much knew what he was, and few were disturbed -- even after Monica showed up. More people were titillated than outraged. As an original FReeper, I watched the anger and disdain focused on Clinton at this forum, but I knew, like Mr. Limbaugh, that Clinton was simply behaving like so many alpha males I had worked for and with. It was just another manifestation of the breakdown of the family and the institution of marriage in this country.
Now if you had asked any of these mainstream philandering alpha males if they would have lied under Clinton's circumstances, they would have said, "Hell, yes!"
Regrettably, Bill Clinton was not that far out of the mainstream.
Zach, powerful men fool around. Powerful men cheat on their wives. Powerful men have always had mistresses, courtesans, geishas, slave girls, concubines, right of the first night, wive's handmaidens, etc. In a country with a 50% divorce rate infidelity shocks no one.
Another point that I wish Publius had mentioned is that I think the American people associate Watergate with the Time of Troubles of weak presidents in the second half of the 70's during which the Senate basically ran the country. How much of the politics of the 70's turned around Senate fights ? Salt II, ERA, Panama Canal Treaty, etc. That is why the American people protected Reagan over Iran-Contra and Clinton over impeachment. The American people did not want a crippled presidency over a bit of tail.