WASHINGTON — Few people in this town know the world like Joe Biden.

The 65-year-old chairman of the Senate Foreign Relations Committee returned recently from a visit to the Republic of Georgia to assess the Russian invasion there. He has visited Iraq more than seven times and has met with the world's most important leaders.

A Roman Catholic, Biden was born in working-class Pennsylvania and appeals to the white, blue-collar voters Sen. Barack Obama is trying to reach in his bid for the White House.

But he also brings certain risks to the campaign. Occasionally, his candor and passion lead to impolitic gaffes.

He apologized last year after calling Obama the first "mainstream African American (presidential candidate) who is articulate and bright and clean and a nice-looking guy" in a newspaper story that ran the day he launched his own presidential campaign.

Some interpreted the remark as racially offensive, but Obama didn't take it personally and defended Biden's commitment to racial equality, saying during a debate, "I have absolutely no doubt about what is in his heart."

During his campaign, Biden, questioned Obama's preparedness and his staff criticized Obama's "Johnny-come-lately" position on combating al-Qaida in Afghanistan and Pakistan.

He abandoned his second presidential bid in January, following a fifth-place showing in the Iowa caucuses.

As the vice presidential nominee, Biden will need to play attack dog for the cerebral Obama. And he has shown he can do it with biting humor.

In one of Biden's most memorable debate moments as a presidential candidate, he said there are only three things former Republican candidate Rudy Giuliani mentions in a sentence: "A noun, a verb and 9/11."

Biden's voting record has been described as moderate to liberal. Though he voted to authorize the war, he has been a sharp critic of Bush's war policies. He opposed the troop surge and has set goals for withdrawal of all combat troops.

Biden counts among his signature accomplishments the 1994 Crime Bill that put 100,000 more police on the street and the Violence Against Women Act, targeting domestic violence and rape. He also authored a Senate-passed resolution endorsing the air war in Kosovo.

He supports the landmark abortion rights decision, Roe v. Wade, but was the only Democratic presidential candidate serving in 2003 to have voted for a ban on late-term abortions.

The first of four children, Biden was born in 1942 in Scranton, Pa., before the family moved to Delaware in 1953.

Though he is known to be loquacious, he stuttered as a child. He overcame it by reciting Yeats and Emerson poetry while looking in the mirror.

He was elected to the Senate at age 29, the fifth youngest senator ever to serve.

Like Obama, Biden was seen as his party's fresh face in 1987, when he first ran for president. That effort collapsed amid charges that he plagiarized a portion of a speech he said he forgot to attribute.

Biden's personal story has been touched by tragedy. A month after he was first elected to the Senate, his wife, Neilia, and infant daughter Naomi suffered fatal injuries in a car accident while Christmas shopping. His sons Beau and Hunter were critically injured but fully recovered.

Beau Biden, the attorney general of Delaware, is scheduled to deploy with his Army National Guard unit to Iraq on Oct. 3.

Joe Biden also survived near-fatal brain aneurysms in 1988 that kept him out of the Senate for seven months.

Biden and his second wife, Jill, have a daughter, Ashley. He rides the train between Wilmington and Washington every day.