Obama's rousing speech gives Clinton's bid a boost as he goes into battle one last time
Barack Obama strode onto the Democratic convention stage in 2004 to deliver his message of optimism as a completely unknown state senator from Illinois.
Twelve years later in Philadelphia, his own race run, he repeated his belief in the "audacity of hope" but framed it in stark contrast to the hate and negativity of Donald Trump.
Mr Obama was greyer for sure - the burden of holding the highest office in the world can weigh heavy - but the old fire was still there as he used his soaring oratory skills to pitch for the woman he defeated in 2008.
Mr Obama laid out the case for voting for the inclusiveness and compassion espoused by Hillary Clinton against the "blame, anger and hate" that was seen in Cleveland last week.
His pitch was not just for the unity of the Democratic Party following divisions earlier this week, but also of the very country itself - threatened by a lurch into the unknown if the unpredictable and divisive Mr Trump wins the White House race.
Describing Mrs Clinton as a "patriot", Mr Obama said she understood the country and that its strength lay in its diversity. People outside the country were baffled by what was happening in this election, he said, painting Mr Trump as a man with no plan, who cared little for facts - but very much about himself.
"We don't look to be ruled," he said, as he continued the theme from his 'brother' Joe Biden earlier in the night of putting the Democrats on the front foot against Mr Trump.
Mrs Clinton will need all the help she can get if she is to overcome the Trump 'movement' - as recent polls have the billionaire businessman in the lead and Mr Obama himself admitted that the Republican could win in November.
Fortunately for her, the cavalry has arrived. Mr Obama was back to doing what he does - and loves - best of all: delivering an inspiring speech and plotting to win an election.
Mr Obama said that he had both rejoiced and mourned with America during his two terms, but had total confidence in the country - and its people - to do the right thing.
He had apparently gone through six drafts of the speech and worked through the night to perfect it, and it showed. It was neatly balanced between trumpeting Mrs Clinton, attacking Mr Trump and looking back on his own journey in the past 12 years.
He said this election was unique, and that it wasn't a choice between two candidates, or left and right, but "a fundamental choice of who we are as a people".
The president energised the Wells Fargo Arena, and left the Democratic faithful with a renewed belief in both their party and the country.
Mrs Clinton joined him on stage at the end, to the roars of the crowd, as she rode the wave of his performance.
It was a world away from Mr Trump's coronation last Thursday, which painted a foreboding vision of a divided, doomed America.
But along with making the case for Mrs Clinton and against Mr Trump, the president's appearance also marked the start of the long goodbye from the public stage for the First Family.
The years in between his Boston convention speech and his performance in Philadelphia could hardly have been imagined back in 2004.
From overseeing the raid that killed the world's most wanted man, Osama bin Laden, and (eventually) passing his signature healthcare reform, to the contentious Iran deal and rebuilding relations with Cuba, Mr Obama's time in office has been triumphant, testing, controversial and, for several reasons, historic.
The world - if not America in its entirety - fell in love with his impassioned speeches, infectious smile, the love and protection he showed to his family and his ability to comfort people at times of crisis.
A president for the social media age, he has that rare ability to connect with young and old, rich and poor, alike.
What the future holds for him is unclear, but it will certainly involve multiple rounds of golf and possibly some university teaching.
The big remaining question is to whom he will be handing over the keys to the White House in January.
For his old rival, Mrs Clinton, the next three-and-a-half months will be a Herculean battle of wills against the formidable and unpredictable Mr Trump.
She is lucky to be able to call on friends in high places. Expect to see more of Mr Obama in the coming weeks as he fights one final campaign.