Final answer:
President Clinton was impeached by the House in 1998 for lying under oath about his extramarital affair with Monica Lewinsky, not the affair itself. He was later acquitted by the Senate and completed his second term.
Step-by-step explanation:
Impeachment of President Clinton
In 1998, Congress brought impeachment charges against President Clinton because he lied about his extramarital affair before the grand jury. The affair was with White House intern Monica Lewinsky, and President Clinton initially denied this relationship. He was charged with perjury and obstruction of justice. The House of Representatives, voting largely along partisan lines, impeached Clinton, but he was acquitted by the Senate and finished his second term as president.
While the affair itself was not the ground for impeachment, it was Clinton's lying under oath to cover it up that led to the House's decision to impeach. The Senate trial was a significant event and was covered extensively by the media, with huge public attention.
Despite the impeachment, President Clinton remained quite popular and left office with a high approval rating, underlining the complex views Americans held about the scandal and the political process involved.