Will the son of an absent Kenyan father and a white mother from Kansas, who split his childhood years between the Aloha State and Indonesia, be lauded for bringing down unemployment, the raid that killed Obama bin Laden, or reforming the health care system?
Will he be praised for revitalizing relations with Cuba or pushing through a global climate agreement?
Whatever the historians write, Obama -- America's first black president -- can certainly claim some bona fide successes.
But one dream got lost along the way: that of national reconciliation.
Years of stalemate with an intractable Republican-led Congress and Donald Trump's shock election win -- which he did not see coming -- at the end of an unprecedentedly aggressive campaign have revealed a deeply divided country.
Political divisions are to be expected, with Republicans and Democrats refusing to work together to the point of sometimes paralyzing government.
But racial fault lines also came to the fore during Obama's presidency, and with an unexpected force.
Careful not to be seen as a "president for black Americans," Obama paradoxically may have been the wrong leader to move the needle on the race issue.
That reality is a bitter pill to swallow for a man who said, in the 2004 speech that put him on the political map, that there is "not a liberal America and a conservative America, there's the United States of America."
"There's not a black America and white America and Latino America and Asian America," he said. "There's the United States of America."
But Obama, criticized by some as too much of a policy wonk and sometimes professorial, may not have taken the pulse of Trump's America -- a mainly white, working middle class terrified by the whirlwind effects of economic globalization.
- Still popular -
With his temples a bit grayer now, Barack Hussein Obama will leave the Oval Office at age 55 with his popularity near his all-time high, much like Ronald Reagan in 1989.
A relative political novice when he ran for president in 2008, promising to transform the United States under his optimistic banner of "Yes we can," Obama entered the White House in 2009, and the learning curve was steep.
Just 47 at the time, four years older than John F. Kennedy, he freely admits he initially underestimated the difficulty of doing business in Washington.
He could only shake his head at how Republicans systematically blocked his every move, even if he himself also lacked a certain sense of flexibility in his dealings with Capitol Hill.
Confronted with economic and financial chaos upon his arrival in office, with huge sectors of industry at the edge of an abyss, he managed to push through an $800 billion stimulus package.
Then, after an epic battle on Capitol Hill, Obama saw his signature health care reform plan -- which became known as "Obamacare" -- become law.
Some 20 million Americans now have health insurance who did not before thanks to the Affordable Care Act, which Trump has pledged to repeal and replace.
- Syria casts a shadow -
Obama leaves behind a mixed record on the foreign policy front.
The surprise Nobel Peace Prize he won in 2009 proved in some ways to be a poisoned chalice.
The Nobel committee lauded his "extraordinary efforts to strengthen international diplomacy and cooperation between peoples" -- after less than eight months in office.
But in accepting the award, Obama acknowledged his accomplishments were "slight" compared to those of the "giants of history" who preceded him.
However, the onetime senator from Illinois can certainly claim to have made a clean break with the Bush years.
He presided over the withdrawal of the vast majority of US troops from Iraq and Afghanistan (from 180,000 to 15,000) and banned waterboarding and other post-9/11 "enhanced interrogation techniques" now widely seen as torture.
By bringing Iran -- Saudi Arabia's Shiite rival -- back into the international fold with a nuclear deal, and by showing that America had other priorities than the Middle East, notably in Asia and Africa, Obama tried to shuffle the deck.
But his prudence and passivity in the face of chaos in war-wracked Syria, which has led to the worst humanitarian crisis since World War II, leaves a shadow over his tenure at 1600 Pennsylvania Avenue.
While rejecting his critics, Obama has admitted he was somewhat powerless.
"It haunts me constantly," he told Vanity Fair magazine last year.
"I do ask myself: 'Was there something that we hadn't thought of? Was there some move that is beyond what was being presented to me that maybe a Churchill could have seen, or an Eisenhower might have figured out?'"
- Highs and lows -
On certain issues, such as climate change, Obama -- a constitutional law expert -- learned how to adapt.
From the immense disappointment of the failed Copenhagen summit in 2009, he figured out that no global action would occur without Washington and Beijing working together.
The Paris accord reached in late 2015 came together in large part thanks to their cooperation.
On other issues, from the Israeli-Palestinian conflict to the military prison at Guantanamo Bay, Obama clearly failed.
Two days after taking office, he signed a decree aimed at shutting down the US prison in Cuba within a year. Eight years later, although it holds far fewer inmates, the detention center is still there.
- 'History zigzags' -
A talented orator, Obama will also be remembered for a handful of powerfully delivered speeches.
In Charleston, where nine black parishioners were gunned down by a white supremacist during a Bible study session, Obama offered a rousing eulogy -- and then began singing "Amazing Grace." The thousands of mourners joined in.
In Athens, he recognized how "democracy, like all human institutions, is imperfect. It can be slow; it can be frustrating; it can be hard; it can be messy."
In Chicago, where he cut his political teeth, he tried in his farewell speech this month to channel the energy of those who elected him in November 2008.
"I'm asking you to believe. Not in my ability to bring about change -- but in yours," he said to cheers -- and some tears.
Conscious that much of his legacy could be picked apart by his successor, Obama has maintained his fierce optimism -- his political calling card, mocked by some and hailed by others -- until the very end.
After Trump's victory, he called on the country to accept that "sometimes, history zigzags" and move forward. It's useless, he said, to "get into a fetal position."
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