An upbeat President Bush (search) set forth an aggressive agenda for the next four years, but he also must deal with the realities his predecessors faced — second terms tend to be disappointments, often marred by scandals, infighting and lackluster performances.

In his second term, Bill Clinton (search) suffered through impeachment by the House and trial in the Senate after his affair with intern Monica Lewinsky. The Iran-Contra scandal (search) and upheaval in his inner circle marred Ronald Reagan's second term.

Richard Nixon rode a 49-state landslide into a second term in 1972 and within two years resigned over the Watergate scandal (search). Dogged by health problems, Republican Dwight Eisenhower watched the Democrats increase their grip on Congress while the Soviet Union took the first leaps in the space race.

"We expect too much. Second-term presidents get careless and cocky. They either overreach, or do something illegal, or don't manage the way they should," said Stephen Wayne, a political science professor at Georgetown University.

Claiming "the will of the people at my back," Bush pledged to bring democracy to Iraq, overhaul the tax code, revamp Social Security, trim the deficit, win enactment of limits on medical malpractice lawsuits, pass an energy bill and create more jobs.

"I earned capital in the campaign, political capital, and now I intend to spend it," he told reporters.

While political veterans say they never would underestimate Bush, especially after his solid victory, they also argue that second terms can be a minefield.

Conservative economist Bruce Bartlett, who advised both Reagan and Bush's father, said Bush should have chosen between revamping the tax code and Social Security — there isn't enough time to overhaul both "even with expanded Republican control of both houses."

"It's a cliche, but it's true, anyway: Presidents become lame ducks the day they're re-elected," Bartlett said.

Furthermore, if Bush does get to name several Supreme Court justices, confirmation battles could tie up the Senate for many months, dimming chances for domestic legislation.

David Gergen, who served in the administrations of Presidents Nixon, Ford, Reagan and Clinton, contends that second terms often come up short because the top-notch individuals brought into office by a new president seldom stick around for eight years, energy ebbs and "anything you really wanted to do, you did in the first term."

In Woodrow Wilson's second term, the Senate rejected his proposal for a League of Nations, and he spent his final months as an invalid after suffering several strokes.

Even Franklin D. Roosevelt, who went on to a record four terms and a multitude of accolades as a World War II leader, had a dismal second term. After winning re-election in 1936, he tried to expand and pack the Supreme Court. It backfired, bringing widespread public scorn and significant Democratic losses in Congress in the 1938 midterm elections.

Democrat Harry Truman served the equivalent of two terms, filling out the remaining 3 1/2 years of Roosevelt's fourth and final term and winning on his own in 1948. But Truman's tenure was marred by a stalemated Korean War and Soviet acquisition of nuclear weapons. He chose not to run again in 1952.

Bush has a small window to accomplish something because members of his own Republican Party "are going to get increasingly preoccupied with 2008, and that includes Bill Frist," said Norman Ornstein of the American Enterprise Institute. Tennessee's Frist, the Senate majority leader, is eyeing a 2008 presidential run.

Many analysts suggest that Bush has his best chance at getting several domestic initiatives through Congress, including an energy bill, an overhaul of the bankruptcy code and malpractice limitation legislation.

But he could find an all-Republican government a mixed blessing.

"His conservative base will expect him to deliver," said Thomas Mann, a presidential scholar at the Brookings Institution. Pushing measures dear to the religious right could limit his bargaining ability on other issues and make him burn through that political capital quickly, Mann said.

Sometimes second-term presidents grow weary of domestic battles and turn their attention to foreign policy challenges, mindful of their legacies.

Fred Greenstein, a Princeton University political scientist, points to Clinton's end-of-term efforts to bring peace to the Middle East and Reagan's outreach to Soviet President Mikhail Gorbachev that helped hasten the end of the Cold War.

"Second terms, in part, are for the history books," Greenstein said.