It must by now be obvious that people in politics have sex, outside of the conventional and sometimes puritanical values presented to the voters. Any list of political love affairs, casual affairs, paid sex, risky or kinky sex, flirtations, same gender sex and multiple marriages would be long, and relatively uncorrelated to political parties or ideologies. It should also be obvious that political figures lie about their sex lives. These lies are told for all sorts of reasons, some self serving, some out of consideration to third parties whose lives are also impacted by candor, and some lies that simply try to establish some boundaries to the public's "right to know."
There is no evidence that the best leaders have the most monogamous or boring sex lives, nor can one argue the reverse.
It is both unrealistic and stupid to insist that politicians "tell the truth" about their sex lives. People lie about sex, and often this is a positive, not a negative. Do you really want to know everything about the sex lives of your parents, your children, their school teachers, the manager of the local Safeway, or your car pool buddies? Why would you want to know everything about the sex lives of members of Congress, judges or Governors?
The best outcome might be to tell politicians to keep their sex lives to themselves. Don't make your happy marriage the center piece of your campaign. Don't volunteer to be interviewed by Wolf Blitzer on CNN about your sexting habits. Don't call excessive attention to your sex life, or lack of a sex life. Don't go on television to condemn someone else's messy sex scandal. But mostly, don't feel obligated to tell the truth, about your sex life. This is not the same as promising to take positions on real policy issues, to get elected, and then immediately changing or abandoning positions, once in office. This is not the same as lying about your resume, lying about the constant trading of special interest legislation for campaign contributions, or lying about matters of war and peace, or the public's civil rights. This is not the same as lying about the countless things that really do impact our lives, and which political figures are given real responsibility and trust.
In short, feel somewhat free to lie about your sex lives. But less free to lie about everything else associated with your job as an elected official.