With rising casualties in Iraq, a widely criticized federal response to Hurricane Katrina, a Supreme Court candidate forced to withdraw her nomination and now the indictment of a powerful administration aide, President Bush's second term may appear to have gotten off to an unusually rocky start.

Historically speaking, however, the administration's struggles since the 2004 election may not be very surprising, given the spotted record of second-term presidencies.

Bill Clinton was impeached, though not convicted. Several close aides to Ronald Reagan were indicted in the Iran-contra scandal. Richard M. Nixon, of course, resigned over Watergate. And Woodrow Wilson couldn't get Congress to ratify the League of Nations and struggled with debilitating health problems.

"It fits into what has been a recent pattern over what has been now 70-odd years," said Chester Pach, a presidential historian at Ohio University. "It's hard to know how it could play out. It could be a real disaster, but it could be a period of temporary reverses."

Alfred J. Zacher, author of "Trial and Triumph - Presidential Power in the Second Term," says that of the 19 presidents re-elected through history, only six can be said to have had truly successful second terms, and even some of them faced significant challenges. The six, according to Mr. Zacher, are George Washington, James Madison, Andrew Jackson, Theodore Roosevelt, Dwight D. Eisenhower and President Reagan.

Several historians attribute the second term problems to a confluence of hubris, overreaching and, oddly, complacency.

Presidents and their staffs are typically triumphant after re-election, especially if they are believed to have won a greater mandate than they did in their first election as Mr. Bush did, leading to a high self-regard among the administration officials.

But there is also a tendency toward complacency and burnout given the incredibly strenuous and taxing workload carried by White House staffers. Realizing that vulnerability, and looking to cement their legacies as great leaders before they leave office, many presidents set what may be over-ambitious goals, said Rick Shenkman, editor of the History News Network at George Mason University. "They want to do something really big."