While neither man’s name will be on any ballot in November, both will be the star attractions for their respective parties, as they seek to use their popularity and fame to help push candidates over the winning line.
And while supporters of each will thrall to the differences between the two - Mr Trump’s off-the-cuff, nationalist bravura, and his predecessor’s more measured, multilateral inclusiveness - both men have the ability to excite and energise an audience.
“I think what will be very interesting is to see what Obama says on immigration, after what has been happening at the border,” Juliette Kayyem, a senior official in the Department of Homeland Security during Mr Obama’s first term, told The Independent.
“I think he will be say that Democrats can be tough on immigration without being cruel.”
Mr Obama this week released a list of 81 candidates - which his office said would be the first batch of several - he is backing for 2018.
“I’m proud to endorse such a wide and impressive array of Democratic candidates - leaders as diverse, patriotic, and big-hearted as the America they're running to represent,” he said in a statement.
“I’m confident that, together, they’ll strengthen this country we love by restoring opportunity, repairing our alliances and standing in the world, and upholding our fundamental commitment to justice, fairness, responsibility, and the rule of law. But first, they need our votes.”
Among the candidates were several people who served either in his administration or his campaign. Around half were candidates for state legislatures, something on which the 44th president has been focussing since he left office in January 2017.
So far, the former president has steered clear of some of the more contentious races; he did not immediately endorse Alexandria Ocasio-Cortez, the Democratic left’s latest star, who recently defeated longtime congressman in the primary contest for New York’s 14th congressional district.
Neither did he weigh in on New York’s race for governor, where incumbent Andrew Cuomo faces a progressive primary challenge from Sex and the City actress Cynthia Nixon.
Among the names he backed for governorships were Jared Polis of Colorado, Gavin Newsom of California, Stacey Abrams of Georgia, Richard Cordray of Ohio and JB Pritzker of Illinois.
Mr Obama’s office said the list was heavy on young and diverse state-level Democrats because the former president “hopes to help current and aspiring Democratic leaders establish themselves, build their profiles, and lead their communities”.
It also said he would try and help the party retake the House of Representatives. Democrats need to flip 23 seats if they are to secure the lower chamber of Congress, which is the place where any impeachment effort of Mr Trump would begin.
The former president has admitted that during his two terms in office, the party failed to properly address defeats in state legislatures and governors’ mansions across the country.
His office said he would be campaigning for some of the candidates he has endorsed, without specifying which or where. Both his office and that of the Democratic National Committee did not immediately respond to enquiries on Thursday.
The announcement followed a move by former first lady Michelle Obama’ who said last month she would help help lead When We All Vote, a non-partisan, not-for-profit group working to help register new voters.
Mr Trump has already been busy campaigning ahead of election day, with recent rallies in Florida, Montana and Iowa. On Thursday night, he was holding a so-called ‘Make America Great Again’ rally in Pennsylvania.
He has also been busy endorsing Republican candidates and claiming credit for those who have won their primaries, among them congresswoman Martha Roby who last month easily defeated a primary challenge from Bobby Bright.
“My endorsement came appropriately late, but when it came the ‘flood gates’ opened and you had the kind of landslide victory that you deserve,” Mr Trump wrote on Twitter. “Enjoy!”
Republicans sought to shrug off Mr Obama’s involvement, saying that Democrats had lost nearly 1,000 political offices around the country under his leadership and then lost the White House in the 2016 presidential election.
“No one’s more to blame for how weak today’s Democratic Party is than President Obama,” said Republican National Committee spokesman Michael Ahrens, according to Reuters.
But polls suggest Mr Obama retains considerable star power, 18 months after he left the White House.
Last month, the Pew Research Centre revealed the findings of a survey which asked people to name who they thought did the best job as president in their lifetime. Mr Obama was the top choice on 44 per cent, ahead of Bill Clinton on 33 per cent and Ronald Reagan on 32 per cent. Mr Trump was placed fourth with 19 per cent.
While Mr Trump has frequently criticised Mr Obama and accused his administration of illegally bugging his campaign during the 2016 White House race, Mr Obama has, as has been the convention for former presidents, been all but silent about the man who succeeded him - something that has angered many in the party.
Last month, in a speech at an event in South Africa celebrating Nelson Mandela’s 100th birthday, Mr Obama was perhaps his most outspoken about Mr Trump.
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