Richard Nixon won a landslide re-election in 1972. Two years later, he resigned in disgrace.

Bill Clinton was impeached -- and although he survived, he accomplished little by way of policy or legislation in his final four years in office. He tried and failed to win fast-track trade authority or campaign-finance reform--both measures Congress passed during George W. Bush's first term.

Ronald Reagan was a partial exception. Under his leadership, Congress passed sweeping tax reform legislation in 1986, and when Mikhail Gorbachev came to power, Reagan was able to change his approach to the Soviet Union.

But Reagan's second term was troubled too. He lost a big political battle with the defeat of Robert Bork's nomination to the Supreme Court. And the arms-for-hostages scandal was a distraction and a blot on his administration.

Why do second terms go bad? Part of it is just the law of averages. It's hard to avoid problems altogether for eight years, and when presidents have unsuccessful first terms, they don't get a second term.

In his second term, George W. Bush may be able to beat the odds. He has two advantages that his predecessors lacked. First, his party controls both houses of Congress. Nixon and Clinton faced Congresses of the opposite party, and Reagan had only a Republican Senate, which he lost in 1986.

Bush's second advantage is that there's no more independent counsel statute. That was the law that gave prosecutors the power to conduct open-ended investigations of Reagan and Clinton, with no limits on their resources. Even when they didn't actually produce any prosecutions, such investigations consumed officials' time and energy and generated bad coverage in the press.

Bush may also benefit because his second term is starting off so much better than his first, when the disputed election left the opposition particularly bitter. Will his clear victory the second time around calm the waters and make it easier to get things done? There's no historical precedent here: Though other presidents have won disputed elections, Bush is the first to be re-elected.