Democratic presidential candidate Hillary Clinton speaks in New York after clinching her party's nomination, June 7, 2016,
Democratic presidential candidate Hillary Clinton speaks in New York after clinching her party's nomination, June 7, 2016,

WHITE HOUSE - Barack Obama is the first sitting U.S. president in several decades who can significantly impact the race to elect his successor. His approval ratings are more than 50 percent.

Administration officials have repeatedly said Obama is extremely eager to help unite the Democratic party and hit the campaign trail to support its presidential nominee.  However, the White House says he will not make an endorsement until after a meeting with candidate Sen. Bernie Sanders on Thursday
“We have got to make sure we get this election right,” Obama told supporters during a recent Democratic party fundraiser in Florida.
“We take for granted the incredible progress that we've made across every dimension of the economy, security, a society that's more tolerant and more accepting of diversity,” he said. “We've got a lot of stuff to build on.”

Supporters for Democratic presidential candidate H
Supporters for Democratic presidential candidate Hillary Clinton hold up campaign logos during a presidential primary election night rally in New York, June 7, 2016..

Former Secretary of State Hillary Clinton, who claimed the Democratic presidential nomination after decisive primary victories on Tuesday, is viewed as someone who can push forward Obama’s work beyond his presidency and help cement his legacy.
Obama is also ready to burst onto the campaign stage to counter controversial rhetoric by Donald Trump, the presumptive Republican nominee.
Trump's own party leaders have criticized some of his remarks as divisive and racist, and the president has said Trump’s foreign policy statements have “rattled” world leaders.

Presumptive Republican presidential nominee Donald
Presumptive Republican presidential nominee Donald Trump speaks during a news conference at the Trump National Golf Club Westchester in Briarcliff Manor, New York, June 7, 2016.

Treading carefully and running 'scared'
Mindful of the need to keep the Democratic Party united and energized to win the November presidential election, the U.S. leader did not step forward immediately to endorse Clinton after her decisive primary victories on Tuesday.
Instead, Obama telephoned both Clinton and her Democratic rival, Bernie Sanders.
The Vermont senator has garnered the support of millions of voters, particularly those under 30, with a consistently forceful message against the corrosive sway of special interests in Washington and rising income inequality in America.
At Sanders' request, Obama will meet with the senator at the White House on Thursday to discuss “how to build on the extraordinary work he has done to engage millions of Democratic voters, and to build on that enthusiasm in the weeks and months ahead," according to a statement by Press Secretary Josh Earnest.
While the president has expressed confidence in the Democratic party’s ability to win the White house and other key races, he has told supporters, “I want us to run scared the whole time.”

Supporters gather to see U.S. Democratic president
Supporters gather to see U.S. Democratic presidential candidate Bernie Sanders speak during a election night rally in Santa Monica, California, June 7, 2016.

Giving Clinton 'sizzle'
Obama congratulated Clinton for securing the delegates necessary to clinch the Democratic nomination

With an unfavorable rating of more than 50 percent in most polls, Clinton has much to gain from the backing of a popular president who is widely respected as a party leader and on the global stage.
“It has been a long time since a sitting president became the super campaign cheerleader for a candidate,” said Douglas Brinkley, Rice University presidential historian.
In 1988, Ronald Reagan had a major impact on George H.W. Bush’s bid for the White House, as did Theodore Roosevelt on William Taft’s victory in 1908.

Clinton is largely viewed as having the ability and experience to serve as president, said Brinkley. But her image has been tarnished by a series of scandals, and she does not possess the same powerful ability to connect with the public as does Obama and her husband, former President Bill Clinton.
“Hillary Clinton is not the most charismatic public speaker. She’s worked on it,” said Brinkley. “But the kind of sizzle factor that President Obama can bring, after winning two terms in a row, will be an immeasurable help to her.”

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Obama is also highly popular among key voting blocs, such as African Americans, Latinos, and younger voters.
“Barack Obama knows how to bring out the college students, in a way that Bernie Sanders did. He’s popular with young people. And she sorely needs to energize younger voters,“ Brinkley noted.
Obama wants to ensure the next president will carry forward his signature accomplishments, like passage of the Affordable Care Act.
“It’s almost like he’s running for a third term for president,” said Brinkley.