Washington (CNN)The transformation of Donald Trump begins Thursday.
The freewheeling, acerbic, often vulgar and offensive maverick of the campaign trail has 70 days to become a president.
Trump will begin the process with a remarkable meeting with President Barack Obama at the White House, an encounter between antagonists who never bothered to hide their visceral dislike for one another.
After his stunning election victory over Hillary Clinton, Trump also has a dizzying list of tasks to fulfill, and the White House meeting is only the start of his hectic agenda before Inauguration Day.
First, the President-elect must make a stab at uniting the country, after a scorched-earth campaign in which he consciously tore at the nation's gender, racial and economic fault lines to build a movement to win power. He's practicing some unusual humility.
"I pledge to every citizen of our lands that I will be the president for the American people," Trump said in his victory speech Tuesday. "For those who have chosen not to support me in the past, for which there were a few people, I'm reaching out to you for your guidance and your help so we can work together and unify our great country."
But his challenges were on clear display Wednesday as protests broke out from Boston to Los Angeles.
Trump's meeting with Obama promises to be one of the most awkward encounters ever between a president and his successor. The President-elect's agenda is diametrically opposed to Obama, including the repeal of his signature health care law.
Trump built his political career and appeal to what eventually became his base with his crusade to prove that Obama was not a natural born citizen and was not therefore eligible for the presidency. Many Democrats found his antics racist and deeply offensive to the first African-American president.
Partly spurred by his contempt for Trump, Obama used the power of his office like no other president before him to make the case on the campaign trail that his potential successor was essentially un-American, unfit for the presidency and too risky to be trusted with the nuclear codes.
"The president made a forceful argument and he stands by that argument, but the time for making that argument has passed," White House spokesman Josh Earnest said Wednesday. "The American people rendered their judgment, and President Obama doesn't get to choose his successor, the American people do, and they did."
Preserving the integrity of American democracy makes it incumbent on Obama to ensure the peaceful transition of power, despite his own deep reservations and antipathy toward his successor.
Trump is also under immediate pressure to build a relationship with Republican leaders, including House Speaker Paul Ryan and Senate Majority leader Mitch McConnell, who have often viewed him with deep skepticism but are now crucial to his agenda .
Trump must build an administration that is ready to hit the ground running January 20. And perhaps his most daunting assignment is building a national security structure from scratch, and bringing his own sketchy foreign policy and national security credentials up to speed.
Every president who walks into the Oval Office faces an adjustment to the inhuman demands of the presidency. Obama is fond of saying that only problems that no one else can solve reach the President's desk.
But Trump is the only man ever to win the presidency with no political, diplomatic or military executive experience, so his learning curve to becoming the most powerful man in the world will be even steeper.
Trump is no longer on the campaign trail and is not therefore subject to the same pressures that a candidate faces. So in a sense, the transition allows him to reset and at least attempt to adopt a more presidential posture.
His task will be exacerbated by the fact that he appears on track to lose the popular vote to Clinton, even though he won the electoral college -- a factor that undercuts any claims of a mandate.
Clinton's 2008 campaign manager Patti Solis Doyle, a CNN contributor, said Trump needs to make amends to Americans insulted by his conduct -- including African-Americans, women and Hispanics.
"I think he needs to start with an apology — honestly," she said on CNN's "The Lead." Given the President-elect's reluctance to admit he is wrong, that step at least seems unlikely.
Trump's new audience stretches beyond Washington and the United States. US allies were alarmed by Trump's victory, given his criticism of US alliances overseas and hazy knowledge of defense and nuclear doctrine.
Adversaries like Russia and China will already be gaming out how best they can take advantage of their inexperienced new counterpart in Washington.
While Trump has the advantage of a ready-made domestic program given Republican control of Congress, he has no such luxury when it comes to national security policy.
Trump's foreign policy team also lacks a diplomatic heavy hitter respected abroad: speculation is mounting that he will bring in someone who is a known quantity overseas as Secretary of State — someone like Sen. Bob Corker, who heads the Senate Foreign Relations Committee.
He has just over two months to staff the State Department, Pentagon, his White House National Security staff, install new leadership at the Intelligence Agencies and begin to install top diplomatic envoys overseas.
It would be a daunting task for any president. Trump is further handicapped by the fact that a huge chunk of the Republican national security establishment, alarmed by his volatile temperament and rudimentary knowledge, defected en masse to Clinton.
But the most fundamental question facing Trump may be his own temperament.
The idea that the President-elect was too erratic and volatile to be commander-in-chief was at the center of Clinton's campaign, and many Americans and foreigners alike worry that his inauguration will usher in a period full of danger and risks.
Trump showed at times on the campaign trail that he could be disciplined. Such a demeanor will be even more crucial now because a stray word from a president who can send financial markets tumbling or send foreign armies onto red alert.
The transition period will be a time for him to try on his new role as a statesman.
The question is whether he will be the version of Trump who vowed to throw Clinton in jail or someone with a personality more becoming of a commander in chief.
"Is this the Donald Trump who wanted to ban all Muslims coming into America?" CNN contributor Matt Lewis, a conservative author, said on CNN Wednesday. "Or is this the Donald Trump that sounded a much more conciliatory last night?
He added: "I hope that he was sort of fronting a little bit to win the election and that he will actually govern in a more statesmanlike manner."