It was perjury in the questioning of Bill Clinton in regard to the Lewinsky affair that led to the impeachment, and Ken Starr was very much in
that picture.
from Wiki:
During the deposition in the Jones case, Clinton was asked,
"Have you ever had sexual relations with Monica Lewinsky, as that term is defined in Deposition Exhibit 1, as modified by the Court?" The judge ordered that Clinton be given an opportunity to review the definition. It said that "a person engages in sexual relations when the person knowingly engages in or causes contact with the genitalia, anus, groin, breast, inner thigh, or buttocks of any person with an intent to arouse or gratify the sexual desire of any person".
[26][27][28] Clinton flatly denied having sexual relations with Lewinsky.[29] Later, at the Starr Grand Jury, Clinton stated that he believed the definition of sexual relations agreed upon for the Jones deposition excluded his receiving oral sex. It was upon the basis of this statement that the perjury charges in his impeachment were drawn up. Clinton was
impeached by the
House of Representatives on December 19, 1998, on charges of
perjury and
obstruction of justice. But despite Republican control of the Senate, Republicans were unable to muster the required two-thirds
supermajority to convict or even simple majority, with 50 Senators voting guilty on the obstruction charge and 45 senators voting guilty on the perjury charge.
Incidentally, Clinton settled with Jones.