Obama casts Clinton as his successor at convention

PHILADELPHIA -- His own legacy on the line, President Barack Obama implored Americans to elect Hillary Clinton to the White House, casting her as a candidate who believes in the nation's future and warning against the pessimism of Republican Donald Trump.

"America is already great. America is already strong," he declared to cheering delegates Wednesday night at the Democratic convention. "And I promise you, our strength, our greatness, does not depend on Donald Trump."

For Democrats, the night was steeped in symbolism, the passing of the baton from a barrier-breaking president to a candidate trying to make history herself.

Obama robustly vouched for Clinton's readiness to be commander in chief, saying, "No matter how daunting the odds, no matter how much people try to knock her down, she never, ever quits."

Earlier Wednesday, Clinton's running mate, Virginia Sen. Tim Kaine, introduced himself to the nation as a formidable foil to Republican nominee Donald Trump.

Democratic vice presidential candidate, Sen. Tim Kaine, D-Va., takes the stage during the third day session of the Democratic National Convention in Philadelphia, Wednesday, July 27, 2016. (AP Photo/Matt Rourke)

With folksy charm, he ridiculed Trump's list of promises and imitated one of the GOP candidate's favorite phrases.

"Believe me!" he said mockingly, as the audience boomed back, "No!"

Obama's vigorous support for Clinton is driven in part by deep concern Republican Trump might win in November and unravel the president's eight years in office.

He warned the billionaire businessman is unprepared for the challenges that would await him in the Oval Office.

Trump fueled more controversy Wednesday when he encouraged Russia to meddle in the presidential campaign.

Vice President Joe Biden speaks during the third day session of the Democratic National Convention in Philadelphia, Wednesday, July 27, 2016. (AP Photo/Carolyn Kaster)

On the heels of reports Russia may have hacked Democratic Party emails, Trump said, "Russia, if you're listening," it would be desirable to see Moscow find and publish the thousands of emails Clinton says she deleted during her years as secretary of state.

Wednesday night's Democratic lineup was aimed at emphasizing Clinton's own national-security credentials.

It was a significant shift in tone after two nights spent reintroducing Clinton to voters as a champion for children and families and relishing her historic nomination as the first woman to lead a major political party into the general election.

The convention's third night was also a time for Democrats to celebrate Obama's two terms in office. Vice President Joe Biden, who decided against running for president this year after the death of his son, called it a "bittersweet moment."

A son of Scranton, Pennsylvania, Biden appealed directly to the working-class white voters who have been drawn to Trump's populism, warning them against falling for false promises and exploitation of Americans' anxieties.

"This guy doesn't have a clue about the middle class," he declared.

Kaine also picked up the traditional attacking role of the presidential ticket's No. 2.

He tore into Trump, mocking his pledges to build a wall along the Mexican border, asking why he has not released his tax returns and slamming his business record, including the now-defunct Trump University.

"Folks, you cannot believe one word that comes out of Donald Trump's mouth," Kaine said. "Our nation is too great to put it in the hands of (a) slick-talking, empty-promising, self-promoting, one-man wrecking crew."

Liberals, particularly those who supported Vermont Sen. Bernie Sanders, have grumbled about Kaine being on the ticket, particularly because of his support for "fast track" approval of the Trans-Pacific Partnership trade pact.

Several delegates held up anti-TPP signs as he spoke.

In a move aimed at broadening Clinton's appeal, New York City Mayor Michael Bloomberg -- an independent who considered launching a third-party bid for president -- endorsed the Democratic nominee.

A billionaire businessman himself, Bloomberg took aim at Trump's bankruptcies, reliance on foreign factories and other economic experience: "The richest thing about Donald Trump is his hypocrisy."

President Bill Clinton, filling the role of devoted political spouse, joined the crowd packed to the arena rafters in cheering the attacks on Trump.

Clinton's campaign believes Trump's unorthodox candidacy will turn off moderate Republicans, particularly women, who worry he's too unpredictable to take the helm in a turbulent world.

They recognize Republicans, as well as many Democrats, have questions about Clinton's character but hope to ease those concerns.

Still, the core of Clinton's strategy is putting back together Obama's winning White House coalition.

In both his campaigns, Obama carried more than 90 percent of black voters, the overwhelming majority of Hispanics and more than half of young people and women.

That coalition was vividly on display in the first two nights of the convention in Philadelphia.

Female lawmakers were featured prominently, along with young activists, immigrants and mothers whose black children were victims of gun violence or killed during encounters with law enforcement.

Gun violence continued as a theme Wednesday night as families of mass-shooting victims took the stage.

Delegates rose in an emotional standing ovation for the mother of one of the victims in last month's Orlando nightclub shooting, who asked why "common-sense" gun policies weren't in place when her son died.

"I never want you to ask that question about your child," Christine Leinonen said.

Capping the somber section of the program focused on gun violence, a group of Broadway singers performed a rousing rendition of "What the World Needs Now Is Love" as the audience sang and swayed in unison.

Clinton's convention has been awash in history, with energized delegates celebrating her formal nomination as the first woman ever to lead a major political party in the general election.

Some supporters of Sanders, her primary opponent, continued to voice their displeasure.

But Sanders, meeting with New England delegates, said, "As of yesterday, I guess, officially our campaign ended."