The Framers did not want the President to be a prime minister serving at the pleasure of, and deriving his authority from, his parliamentary party. His authority comes directly from the people, who elect him on a separate ballot from the legislature. In that last case principle would yield to personal necessity. The Constitution does not require you to destroy yourself. Assuming that there are no further revelations, Mr. President, at this point impeachment looks unlikely.
Public opinion is still strongly against it.
So is political logic. The Republicans don't want to run against President Gore in 2000. It is in their political interest to weaken you, not to drive you from office. This scandal is about sex, Mr. President. Even if you did lie in the Jones deposition, you were lying about sex.