DNC 2016: Barack Obama to say only Hillary Clinton knows what it takes to be president. 'She's been in the room'

In a speech that aides began composing last month, President Barack Obama will insist to delegates in Philadelphia on Wednesday that, “there has never been a man or a woman more qualified than Hillary Clinton to serve as President of the United States”.

“You know, 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," Mr Obama will say in a speech set to last thirty minutes. Aides say he was up until 3 am on Monday putting final touches to the draft and practised delivering it in the White House Map Room on Tuesday afternoon.

Brief excerpts of the speech were released by the White House press office several hours before the President was due to deliver the primetime address of the third night of the Democratic convention in Philadelphia's Wells Fargo Center on a day that had been dominated by news of Donald Trump, the Republican nominee, inviting Russia to try to unearth what he said were the 30,000 emails still not handed over by Ms Clinton in the investigation of her use of a private email serve while she ran the State Department.

The stakes are high for the president and his party’s nominee. It will be one of the last times America sees Mr Obama make a set-piece address before he leaves his office next January. For Ms Clinton, his words may count for more than anyone else’s in helping a wary nation accept her as the right person to succeed him in November over MrTrump.

Mr Obama, who has chosen largely to duck the traditional, big-scale donors’ meet-and-greet parties that are largely expected of a party leader at convention time, was to fly into Philadelphia on Air Force One while the convention was already in session hearing speeches from headliners like vice presidential nominee, Senator Tom Kaine.

Also on the docket to take the stage: Joe Biden, who has served as vice president for two terms, and the former Mayor of New York, Michael Bloomberg. Although Mr Bloomberg was originally elected as mayor as a Republican he decided to speak up for Ms Clinton at the confab because of his deep dismay with Mr Trump.

Mr Obama was to use the speech in part to push back against the Trump depiction of the United States as a nation in decline and permanent crisis. “The America I know is full of courage, and optimism, and ingenuity,” he was to say. “The America I know is decent and generous.”

“As I’ve traveled this country, through all fifty states; as I’ve rejoiced with you and mourned with you, what I’ve also seen, more than anything, is what is right with America. I see people working hard and starting businesses; people teaching kids and serving our country. I see a younger generation full of energy and new ideas, unconstrained by what is, and ready to seize what ought to be.”

But above all, he will offer his own appreciation of Ms Clinton, the rival he defeated in the hard-fought primaries of 2008 but whom he later picked as his first Secretary of State.

“Even in the middle of crisis, she listens to people, and keeps her cool, and treats everybody with respect,” Mr Obama was to tell delegates. “And no matter how daunting the odds; no matter how much people try to knock her down, she never, ever quits.

“That’s the Hillary I know. That’s the Hillary I’ve come to admire. And that’s why I can say with confidence there has never been a man or a woman more qualified than Hillary Clinton to serve as President of the United States of America.”