BY TOM RAUM

Associated Press

WASHINGTON

More often, they're fraught with peril, frequently marred by scandal, failure, hubris, and burnout, and souring relations with Congress.

President Barack Obama acknowledges the dangers of overreach, but vows to steer cautiously. The odds are against him.

He's the 20th U.S. president to serve all or parts of two terms. Most of the others have encountered setbacks and frustrations.

He's also the third in a row to win a second four-year term. Both predecessors stumbled.

President Bill Clinton was impeached by the House over lying about an affair with White House intern Monica Lewinsky, although the Senate declined to remove him from office. President George W. Bush failed to get a big Social Security overhaul through Congress and was slammed for his handling of Hurricane Katrina and growing voter anxiety over the Iraq and Afghanistan wars.

From Inauguration Day, a two term president's influence and power begin to ebb.

"It's called fatigue, people burn out. Typically, the top people are recruited for the first term. For the second term, you kind of go to the bench," said Ross Baker, a political science professor at Rutgers University. "It's a little less illustrious than the starting lineup. You're going to get more people perhaps a little less sure-footed. That's putting it, perhaps, mildly."

There's something of a political Continental Divide with second terms. At some point, everybody's attention starts flowing in the other direction as those in both parties start shifting their focus to the next election.

Also, Obama sets out against a backdrop of looming new fiscal showdowns that will come to a head in March--another battle over the debt limit, mandatory spending cuts postponed from January and the expiration of spending authority for the entire government.

And some of his top second-term goals such as immigration and tax-code overhaul, gun control and climate-change legislation come as grim budget realities cast a long shadow over what he can accomplish.

History is littered with troubled second terms.

Richard Nixon resigned in disgrace. Ronald Reagan's second term was marred by the Iran-Contra guns-for-hostages scandal.

Even George Washington, the nation's revered first president, had an ugly second term.

His backing of the Jay Treaty expanding trade ties with Revolutionary War foe Britain divided the nation. Many leaders--including future president Thomas Jefferson--challenged Washington. Jefferson called the treaty a "monument of folly." Angry crowds gathered outside Washington's house and talk simmered of impeachment.

Franklin D. Roosevelt was able to win four terms but had a tumultuous second one despite a 1936 re-election landslide. His effort to expand and pack the Supreme Court with ideological allies was soundly rebuffed by Congress. And Democrats suffered mightily in the 1938 midterms.