Sen. Barack Obama has traveled to the Democratic National Convention arena, making an unscheduled and unscripted appearance to join the party in celebrating his historic presidential nomination.

Obama joined the newly-nominated vice presidential candidate Sen. Joe Biden on the platform and they hugged and applauded each other and the convention delegates.

Obama told the roaring crowd that he wants people to understand why he is proud to have "the whole Biden family on this journey with me to take America back."

He deadpanned at one point that he thought the convention had "gone pretty well so far."

Joe Biden was nominated for vice president Wednesday night and declared that the challenges America faces require "more than a good soldier" in the White House, hailing Barack Obama as a wise leader who can deliver the change the nation needs.

In a single sentence, Obama's new running mate complimented John McCain's years of military service and slapped his claim on the presidency.

The Democratic National Convention approved Obama's chosen running mate by acclamation. Biden accepted with a summons to voters to elect Obama, formally nominated for president earlier in the day, as the nation's 44th president.

The Delaware senator told the convention he'd learned a lot about Obama by campaigning against him for the party's presidential nomination. Biden was an early dropout in that campaign, quitting after he managed only 1 percent of the vote in Iowa's opening caucuses.

Biden said that in debating Obama, watching him react under pressure, he learned about the strength of the Democratic presidential candidate's mind and his ability to touch and inspire people.

Former President Clinton forcefully endorsed Barack Obama's bid for the White House on Wednesday, telling delegates to the Democratic convention that Obama is "ready to lead America and restore American leadership in the world."

Clinton pushed back on attacks — initiated by himself and his wife during the bitter primary campaign, and later taken up by Republican John McCain, that Obama is ill prepared for the White House, especially on matters of national defense.

"With Joe Biden's experience and wisdom, supporting Barack Obama's proven understanding, insight, and good instincts, America will have the national security leadership we need," Clinton said.

Barack Obama swept to the Democratic presidential nomination Wednesday night, a transforming triumph that made him the first black American to lead a major party into the fall campaign for the White House. Thousands of national convention delegates stood and cheered as they made history.

Former rival Hillary Rodham Clinton asked Democrats in the convention hall to make their verdict unanimous "in the spirit of unity, with the goal of victory." And they did, with a roar.

Competing chants of "Obama" and "Yes we can" surged up from the convention floor as the outcome of a carefully scripted roll call of the states was announced.

Obama, a 47-year-old Illinois senator, was across town as the party handed him its top prize — a ticket into the general election campaign against Republican Sen. John McCain. He was expected to briefly visit the Pepsi Center later in the evening to thank the delegates.

Hillary Rodham Clinton summoned millions of voters who supported her in the primaries to send Barack Obama to the White House Tuesday night, declaring in a Democratic National Convention speech that the man who defeated her "is my candidate and he must be our president."

In a prime time address, the former first lady added, "we don't have a moment to lose or a vote to spare."

The packed convention floor became a sea of white "Hillary" signs as the New York senator strode to the podium, and thousands of Democrats cheered as she took a pre-speech sip of water.

While her prepared remarks included a full-throated endorsement of Obama, she did not indicate whether she would have her name placed in nomination or seek a formal roll call of the states when the nomination is awarded by delegates on Wednesday night.

Calling herself a "proud supporter of Barack Obama, she dismissed Republican John McCain with a few choice words.

"No way. No how. No McCain," she said as the hall erupted in cheers.

Former Virginia Gov. Mark Warner, keynoting the Democratic National Convention, said Tuesday night that American voters "have one shot to get it right" by electing Barack Obama president to end Republican leadership that is stuck in the past.

Warner rebuked President Bush and GOP nominee-to-be John McCain, but his address was hardly a summons to political arms against them. He mentioned McCain's name only twice, and he said he'd learned in the cell phone business that made him millions that a strategy of tearing down the competition doesn't suffice.

"I know we're at the Democratic convention, but if an idea works, it really doesn't matter if it has an R or a D next to it," Warner said. "Because this election isn't about liberal versus conservative. It's not about left versus right. It's about the future versus the past."

Pennsylvania Sen. Bob Casey invoked his late father's name Tuesday night and referred to his own opposition to abortion rights from the podium of the Democratic convention — 16 years after his father was denied the same privilege.

While he spoke only briefly during the speech on the issue of abortion, it was intended to send a message: Sen. Barack Obama supports abortion rights, but accepts those like Casey who oppose abortion rights.

In 1992, Casey's father, the late Pennsylvania Gov. Robert P. Casey, was denied a prime-time slot to speak in opposition to abortion rights, which created a rift within the party.

"Barack Obama and I have an honest disagreement on the issue of abortion," Casey said. "But the fact that I'm speaking here tonight is testament to Barack's ability to show respect for the views of people who may disagree with him."