From the Washington Post:

Ensign is considered a leading voice among social conservatives in the G.O.P. In 1998, as a House member running against Reid, he called on President Bill Clinton to resign after revelations about his affair with a White House intern. “He sent taxpayer-paid staff out to lie for him, and that is a misuse of office,” Ensign said, adding that the president had “no credibility left.”

In September 2007, Ensign called then-Sen. Larry E. Craig (R-Idaho) “embarrassing” after Craig was arrested in an airport men’s restroom and pleaded guilty to disorderly conduct in a sex sting. Ensign played the leading role in an unsuccessful effort to force Craig into resigning from the Senate immediately.

Ensign’s affair began a few months after he called for his colleague to resign, according to a timeline provided by his office.

By the way, public records show that Cindy Hampton, Ensign’s girlfriend, got paid about $2,000 by the senator’s campaign in 2008–$1,000 for consulting, $1,041.95 for accounting, and $41.95 for “payment of utilities” (given the repetition of the $41.95 figure, you have to wonder if she didn’t double-bill on utilities. That said, this is obviously the least of Ensign’s problems). The nature of the consulting was not disclosed. Her husband, Douglas Hampton, was paid well while the senator slept with his wife–as an administrative assistant to Ensign, he received $144,146.71 for his work during 2007 and 2008.