They often die hard, as in the case of another present (and past) presidential hopeful, Newt Gingrich, whose earlier infidelity with his current wife haunts his attempted political resurrection as she campaigns cheerfully at his side.
Even former President Bill Clinton's efforts on behalf of his wife Hillary in 2008 almost always were accompanied by news-media references to his own sexual strayings, which contributed heavily to his impeachment by the House of Representatives in 1998. Mr. Clinton miraculously survived several rounds of such scandals while running for president and in the White House, though lesser lights in politics have seen dalliances snuff out their careers.
Nevertheless, in terms of public tolerance, the country has come a long way from the days when Adlai Stevenson, as a divorced man running for president against Dwight D. Eisenhower in 1952 and 1956, was considered unacceptable by many voters. And in 1964, Nelson Rockefeller's failure to gain the Republican nomination was widely attributed to his recent divorce from his longtime wife and marriage to a younger woman.
In more recent years, the political problem with such "scandals" has not been so much a question of morality as it has been of willful deception. What has harmed politicians caught up in allegations of sexual harassment or abuse has been the attempted cover-up, when candor at the outset may have taken much of the sting out of the accusations.
That was a key lesson of the botched Watergate affair. Richard Nixon was undone not only by the plot to break into the Democratic National Committee and the hush money payoffs to the burglars hired by the Nixon re-election committee. His aggressive efforts to cover up the whole mess were what nailed him in the end.
Nixon may be remembered by many Americans for having blurted out in an appearance at, of all places, Disney World in Florida, "I'm not a crook." And Mr. Clinton's dodges -- "I did not have sexual relations with that woman, Miss Lewinsky" and "it depends on what the meaning of the word 'is' is" -- will live long after him.
Yet many subsequent politicians have been brought down by failure to abandon such evasions and just come clean. Rather incredibly under the circumstances, Herman Cain has already been wounded with too many self-inflicted cuts: First he stated flatly that he had never been accused of any sexual harassment, then that he knew nothing about any settlement payments in the case, and more waffling followed.
A cardinal rule in politics, repeatedly emphasized by experienced practitioners of damage control, is get the facts out yourself before others get out their version. In one of the largest presidential scandals of all, it was reported in 1884 that Gov. Grover Cleveland of New York, running for president, had fathered an illegitimate child. When a close friend and Democratic aide, Charles Goodyear, asked him what his reply should be, Cleveland sent him a three-word telegram: "Tell the truth."
Cleveland proceeded to do just that himself, acknowledging the paternity of the child and thereafter assuming responsibility for the care and education of the young boy. During the fall presidential campaign, supporters of Republican nominee James G. Blaine chanted the refrain: "Ma, Ma, where's my Pa? Gone to the White House! Ha, Ha, Ha!" But Cleveland was elected.
Tell the truth was advice that Nixon rejected, had he ever heard it at all. Mr. Clinton received the same advice as well, but he lived up to his reputation as "Slick Willie" and was saved only by fellow Democrats in the Senate who, holding their noses, voted for his acquittal.
Mr. Cain faces the same challenge now, to get the full story out and live up to his reputation for candor whatever the consequences. Vindication could keep his political fortunes alive if indeed his side of the story is told and holds up in the light of day.
Jules Witcover is a syndicated columnist and former long-time writer for The Baltimore Sun. His email is firstname.lastname@example.org.