Democratic presidential nominee Hillary Clinton addresses the Democratic National Convention via a live video feed from New York during the second night at the Democratic National Convention in Philadelphia, Pennsylvania, U.S. July 26, 2016.
Democratic presidential nominee Hillary Clinton addresses the Democratic National Convention via a live video feed from New York during the second night at the Democratic National Convention in Philadelphia, Pennsylvania, U.S. July 26, 2016.

U.S. Vice President Joe Biden has taken the stage on the third day of the Democratic National Convention in Philadelphia, to praise his boss, President Barack Obama, and to tout the qualifications of the party's 2016 presidential nominee, Hillary Clinton.

Biden told delegates Wednesday night that no one is more passionate about this country than Clinton. It's her life story, he said.

Obama is the featured speaker of the night, and will tell Americans why he thinks Hillary Clinton, his one-time secretary of state, should replace him in the White House when he leaves office next January.

In excerpts of remarks issued hours before his speech, the president said there has never been anyone, man or woman, more qualified than Hillary Clinton to be president.

"Nothing truly prepares you for the demands of the Oval Office.  Until you’ve sat at that desk, you don’t know what it’s like to manage a global crisis or send young people to war.  But Hillary’s been in the room; she’s been part of those decisions.  She knows what’s at stake in the decisions our government makes for the working family, the senior citizen, the small business owner, the soldier, and the veteran.  Even in the middle of crisis, she listens to people, and keeps her cool, and treats everybody with respect.  And no matter how daunting the odds; no matter how much people try to knock her down, she never, ever quits."

Obama has already made one joint campaign appearance with Clinton. He plans to spend much of October rallying voters to her side in the weeks before her November 8 national contest against Republican Donald Trump, a real estate mogul seeking his first elected office.

It is a switch from 2008, when Obama defeated Clinton in a months-long race for the Democratic presidential nomination, and then named her as the country's top diplomat after he won the presidency.

President Barack Obama and Democratic presidential
FILE - President Barack Obama and Democratic presidential candidate Hillary Clinton embrace during a campaign rally in Charlotte, North Carolina, July 5, 2016.

In his final months as the American leader, Obama is particularly aware of his legacy and knows that Clinton, a kindred politico with similar views on fighting terrorism, immigration, health care, abortion, gay rights and climate change, would leave many of his policies in place, while Trump has pledged to almost immediately undo them.

Tough words for Trump

Obama in recent days has increasingly disparaged Trump's candidacy, but told NBC News that his election is possible. Trump, a one-time television reality show host, has edged ahead of Clinton in some national political surveys after claiming the Republican nomination last week.

"It is the nature of democracy that until those votes are cast and the American people have their say, we don't know," Obama said of Trump's chances of becoming the American leader. But Obama said that while Clinton "has put out very specific plans and programs and is telling you exactly what she's going to do," Trump has not.

"What I think is scary," Obama said, "is a president who doesn't know their stuff and doesn't seem to have an interest in learning what they don't know.

"I think if you listen to any press conference he's given, or listen to any of those debates, basic knowledge — about the world or what a nuclear triad is or where various countries are or, you know, the difference between Sunni and Shia in the Muslim world — those are things that he doesn't know and hasn't seemed to spend a lot of time trying to find out about," Obama said.

Trump, at his news conference, said Clinton has been "bought and sold 100 percent by special interests and lobbyists. It's going to be four more years of Obama, and a lot of people think that will be worse."

Bill Clinton’s address

On Tuesday night, Clinton's husband, former President Bill Clinton, offered an impassioned speech for her, recounting his courtship of her in the 1970s while they were in law school and family life with their daughter, Chelsea, through the past 30-plus years.

Former President Bill Clinton speaks during the se
Former President Bill Clinton speaks during the second day of the Democratic National Convention in Philadelphia, July 26, 2016.

He told the convention in Philadelphia, Pennsylvania, and a national audience that his wife "is uniquely qualified to seize the opportunities and reduce the risk we face, and she is still the best darn change-maker I have ever known."

At the end of the evening, 43 pictures flashed across a screen at the convention, each showing one of the men who has served as president of the United States, along with that of Obama, the country's 44th chief executive. The screen then shattered into virtual pieces, revealing Hillary Clinton, via satellite from New York.

"It's been a great day and night," she said. "What an incredible honor you've given me." She said Democrats had put the "biggest crack" yet in the so-called glass ceiling preventing women from advancing to higher jobs. Clinton spoke about the significance of the moment to any young girls who were watching.

Hillary Clinton officially secured the nomination Tuesday when Bernie Sanders closed the customary roll call of states by asking the convention to select her by acclamation, or unanimous vote. Clinton did the same in 2008 in support of her then-rival, Obama.

But the move by Sanders did not go over well with some of his supporters, who staunchly oppose Clinton and have not accepted his calls for them to support her. Several hundred of them walked out of the convention hall and staged a sit-in protest.