A sitting president became embroiled in public controversy over private conduct. Political polarization, which had been building with Clinton's 1992 election and the Republican takeover of Congress two years later, crested in intensity. It resulted in entrenchment that still is a terrain obstacle to progress on key national issues.
Clinton's conduct with the 21-year-old Lewinsky, though morally disturbing, wouldn't have threatened his presidency by itself. The danger came when he was accused of lying to a grand jury and later was impeached by the House of Representatives. A Senate trial returned verdicts of not guilty.
Vice President Al Gore's bid to succeed Clinton in 2000 was hampered by public fatigue from the previous two years. Gore's loss was history changing, as his presidency certainly would've been different than President Bush's.