If I have to choose between a President who lies about his sex life or one who lies or otherwise breaks the law in the performance of his official duties, I'll go with lies about sex every time. When it comes to lying under oath, I am also a little more concerned about fulfilling the President's oath of office than about perjury in a trumped up trial financed as part of a conservative vendetta.
Unfortunately, we seem too willing to accept lying from our Presidents in their official capacity as long as we agree with their messages. The Bush administration systematically mislead the people to gain support for the Iraq invasion. It systematically flaunted the law in its treatment of captives and its implementation of surveillance activities. When overturned by the courts, it simply ignored the decisions. Those, in my mind, are actions that directly violate the Presidential oath of office and constitute crimes.
I don't consider Bush Sr's statements about taxes during the campaign to have been a crime in any way at all. It was a campaign promise that he could not keep without disastrous consequences. What he ended up doing was to honor his responsibilities as President and make a tough decision. It cost him his job, but that has to be a secondary consideration.
Reagan's deals in the Iran Contra affair clearly rose to the level of crimes in the performance of his official duties as President. Once again, these were much more serious than questions of sleeping around and lying about it. The Democrats clearly had the votes to push through an impeachment, but never considered it.
We have had three Presidential impeachments proceedings in our country's history: Andrew Johnson, Richard Nixon, and Bill Clinton. In two of the three, Johnson and Clinton, the circumstances were clearly charges that, while technically correct, were fabricated by a determined opposition to overturn an election. Only one, the impeachment of Nixon, was actually a case where a President clearly abused his office for criminal purposes on a systematic basis. All three of the impeachment proceedings have failed to result in a single conviction, with Nixon's being ended only by his resignation.
I suspect that the majority of our Presidents did things in office that could have been used as a technical basis for impeachment. If that becomes the norm whenever the President and Congress are at odds, our political system will collapse into civil war.