Barack Obama had always intended to sit out the first presidential election of his post-presidency, taking heed of the private guidance given to him from Presidents George W. Bush and George H.W. Bush.
Barack Obama vastly preferred governing to campaigning, his friends have long known, so they believed him when he said he looked forward to watching from the sidelines. But those plans were tossed aside by the election of President Donald Trump and his first term in office.
Barack Obama is poised to return to the campaign trail here on Wednesday, making his first in-person appearance in his effort to help Joe Biden in the waning days of his bid for the White House. If the election of Trump was a reaction to the Obama presidency, the November race offers another opportunity to take the country's measure of the men.
"Former presidents tend not to delve too deeply into politics and certainly not the politics of their successors," David Axelrod, a longtime adviser to Obama, said in an interview. "I think that was his plan, but Trump changed that plan."
The campaign stop by Obama is the first in a handful of visits to battleground states where voting is already underway, where Barack Obama will try and rally support for Biden, particularly trying to boost enthusiasm among Black men, Latinos and younger voters.
"He doesn't view it as a personal grudge match with Trump," said Axelrod, a CNN contributor. "He views it as an existential matter for the country and for democracy."
It's been 20 years since Obama lost an election -- at least one with his name on the ballot.
Yet his record is far less successful when he is not a candidate himself, a point illustrated most recently in 2016, when he campaigned aggressively for Hillary Clinton and in 2010 and 2014, when he suffered the same fate most sitting presidents do when their party endures a midterm-election drubbing.
Barack Obama 's appearance here in Philadelphia, following a series of virtual campaign events for Biden throughout the summer, will once again test the power of his appeal and reveal whether his popularity is transferable -- even to his friend and former partner in the White House.
"I trust him to be a great president," Obama said in a video message Tuesday night on Twitter. "He's different. He's on the right side of the issues. He'll get the job done."
Questions over whether a Biden presidency would effectively be a third Obama term have long ago been overtaken by a broad desire to defeat Trump from all wings of the Democratic Party. The policy differences aired during the primary fight -- from which Obama intentionally worked to keep his distance -- have been set aside, for now at least.
Two weeks before Election Day, Barack Obama is injecting himself squarely into not only the presidential campaign, but also key contests that could help Democrats win control of the Senate. He's appearing in four separate television ads for candidates in Maine and Michigan, South Carolina and Georgia, with other contests likely to be added.
"Make sure if Joe Biden wins," Obama said in one spot, "he'll have a Senate ready to work with them to move our country forward."
The demand for Barack Obama is remarkably high, with some Democrats quietly wondering why he hasn't been even more visible during this high-stakes campaign season, especially after he traveled extensively for Clinton in the closing months of the 2016 election.
But even as he worked to finish his biography, which is scheduled to be released two weeks after the election, aides say he has worked aggressively on many virtual efforts from fundraising to taping early-voting videos to endorsing down-ballot candidates.
"In terms of his value, it's been smart not to overuse him," Axelrod said. "They've been using him in targeted digital appeals to constituencies that Democrats need to arouse in this election: young people and people of color, who did not come out in the numbers that Hillary Clinton had hoped four years ago."
Biden, who speaks regularly with Barack Obama, dismissed questions about whether the former President has been sufficiently active in this race.
"He's doing enough for our campaign," Biden told reporters last week. "He'll be out on the trail and he's doing well."
To be sure, Obama has picked his spots during the general election, but has steadily ramped up his efforts and his anti-Trump rhetoric. His comments about his successor may stand out, at least in the recent history of presidents, but Trump has targeted Obama like few others, including falsely questioning his American citizenship for years.
At the funeral of civil rights icon Rep. John Lewis, the former President delivered an impassioned speech that was, at the time, his more forceful rebuke of Trump to date.
"George Wallace may be gone, but we can witness our federal government sending agents to use tear gas and batons against peaceful demonstrators," he said, referring to the racist Alabama governor who ran for president in 1968.
A few weeks later, in his primetime address to the Democratic National Convention, Obama said he had hoped Trump "might show some interest in taking the job seriously" and "discover some reverence for the democracy that had been placed in his care."
"Donald Trump hasn't grown into the job because he can't," Obama said. "And the consequences of that failure are severe."
For the last four years, aides said, Barack Obama has seen a large part of his role as being a unifying figure for the Democratic Party.
He stayed almost entirely out of the Democratic primary battle, only entering the fray for a handful of fundraisers where he offered some tough love to the party's left wing by warning candidates to "pay some attention to where voters actually are" and not where activists voices on Twitter would like to push Democrats.
Once the primary ended and Biden was the presumptive nominee, Barack Obama used his relationship with Vermont Sen. Bernie Sanders, the final Democratic candidate standing against Biden, to help draw the competition to a close. The two spoke multiple times in the weeks leading up to Sanders' decision to get out of the race, sources told CNN at the time.
Even after the primary, however, Barack Obama remained careful in the way he went after Trump, hueing to a long-held belief that former presidents should avoid being overly critical of their successors. When Obama officially endorsed Biden in April, he did so by touting his one-time vice president and only criticizing Trump obliquely, without mentioning his name.
Yet there is no escaping the animosity and tension between Trump and Obama.
At his rallies, Trump continues to vilify Obama and his administration, offering no evidence to back up the unfounded accusations about spying on his campaign four years ago. Trump has repeatedly called for Obama to be indicted, which has fallen flat even to the Justice Department and Attorney General Bill Barr.
As popular as Barack Obama is among Democrats and many independent voters across the country, he also remains a motivating force for Trump's base. Given that history, the final two weeks of the campaign are poised to be highly combustible between the 44th and 45th presidents of the United States.
"He's always understood if he was out there constantly, people would want to turn this into a Trump-Obama race," Axelrod said. "It wouldn't be fair to Biden and it wouldn't be helpful to Biden."
But in the final stretch of the race, Biden aides say, Obama could be the most helpful closer of all.