PHILADELPHIA (AFP) - President Barack Obama steps onto the Democratic convention stage on Wednesday (July 27) US time (Thursday Singapore time) to champion former political foe Hillary Clinton, defend his own legacy and bury Donald Trump's chances of reaching the White House.
Obama will address the penultimate night of the party convention in Philadelphia, making the case that America's first black president should be followed by its first female president.
Clinton on Tuesday became the first woman to win the presidential nomination of a major US political party, teeing up a November showdown with Donald Trump.
Democrats had "put the biggest crack" yet in the glass ceiling for women, she said in a video message to the convention.
Delegates earlier heard a deeply personal testimonial from former president Bill Clinton, who described a great friend, wife and mother who suffers the slings and arrows of politics to be "the best darn change-maker" Americans could hope for.
The current commander-in-chief is likely to offer a harder edge.
Expect Obama to "focus on how Secretary Clinton has the judgment, the toughness, and the intellect to succeed him in the Oval Office," said White House spokesman Eric Schultz.
In the twilight of his second term, Obama faces ever-dwindling opportunities to address the nation, mould his legacy and influence the 2016 race.
But on Wednesday, the 44th president has a prime-time chance when he appears before thousands of delegates in Philadelphia and tens of millions of viewers at home.
The White House says Obama has been working on his speech for weeks.
Yet this touchstone presidential moment has been a decade or more in the making.
The address will bookend Obama's career-launching address to the Democratic convention in 2004, his contentious 2008 primary battle with Clinton and his eight years in the White House.
Aides said Obama will make a familiar case for what has been achieved during his presidency, highlighting America's recovery from the Great Recession.
That is something the White House believes Obama does not get enough credit for.
Obama will also try to leverage his vast popularity among Democrats to unify a party scarred by the bruising primary campaign between Clinton and leftist Bernie Sanders.
The four-day confab in the City of Brotherly Love has so far been anything but fraternal.
Despite entreaties from party leaders, Sanders' supporters have booed a pastor who mentioned Clinton's name and even jeered Sanders when he did the same.
Having fought his own bitter primary against Clinton eight years ago, Obama could offer a conciliatory message.
But so far in the campaign, Obama's most potent role has been as a foil to Trump.
US presidential elections often throw up candidates who are the mirror opposites of the incumbent. That is almost cartoonishly true in 2016.
Where Obama is deliberative, Trump shoots from the hip. Where Trump speaks in staccato jabs, Obama's oratory is sweeping.
The White House is quite literally betting the house on accentuating those differences.
"One force at work here is negative partisanship," said Geoffrey Skelley of the University of Virginia Center for Politics.
"More voters may be voting against something than voting for it."
Obama has already tried to convince voters that Trump does not have the judgment or demeanour to be commander-in-chief.
The 44th president has contrasted the seriousness of the task at hand - fighting the Islamic State in Iraq and Syria (ISIS) group, addressing horrendous levels of gun violence, healing racial divides - with the tone of Trump's insult-laced populist campaign.
Delegate-goers got another dose of that message on Monday, when First Lady Michelle Obama spoke.
"I want someone with the proven strength to persevere, someone who knows this job and takes it seriously, someone who understands that the issues a president faces are not black and white and cannot be boiled down to 140 characters," she said.
While the White House has posited a Clinton win as a third Obama term, a Trump presidency would almost certainly unpick key parts of Obama's legacy.
But this election is also deeply personal for the Obamas.
Trump's assertion that "our country is totally divided" at times seems like a personal repudiation of Obama's credo and his journey.
As the son of a black Kenyan father and white mother from Kansas - as a community organizer who became president, Obama told the 2004 convention in Boston, "in no other country on Earth is my story even possible."
That speech launched Obama's national political career. Since then, it has been an article of faith for Obama that America works better together.
"There's not a liberal America and a conservative America; there's the United States of America," he told delegates.
"There's not a black America and white America and Latino America and Asian America; there's the United States of America." According to Schultz, "it's a principle that has animated the president's lifetime of public service." Obama is likely to once again ask Americans to bet on change, this time in the form of a first woman president.