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.

These are Trump's key promises for his first 100 days

These are Trump's key promises for his first 100 days 01:02

These are Trump's key promises for his first 100 days

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.

Photos: Anti-Trump protests after election Nearly 1,000 students and faculty members at Rutgers University staged a rally in downtown New Brunswick, New Jersey, to protest President-elect Donald Trump on Wednesday, November 16. At least 25 US cities have seen protests since Trump won the presidential election. Hide Caption 1 of 30 Photos: Anti-Trump protests after election Students hold signs in front of the Supreme Court in Washington during a protest on Tuesday, November 15. Hide Caption 2 of 30 Photos: Anti-Trump protests after election Activists use a banner to block traffic on Interstate 395 during an anti-Trump protest in Washington on Monday, November 14. Hide Caption 3 of 30 Photos: Anti-Trump protests after election Anti-Trump protesters in New York hung an upside-down American flag from the side of the Manhattan Bridge on November 14. Hide Caption 4 of 30 Photos: Anti-Trump protests after election Demonstrators distribute safety pins as a sign of solidarity against intolerance during a rally against Trump in New York on Saturday, November 12. Hide Caption 5 of 30 Photos: Anti-Trump protests after election Demonstrators march to Trump Tower in Chicago on November 12. Hide Caption 6 of 30 Photos: Anti-Trump protests after election People protest Trump during a march in downtown Miami on Friday, November 11. Hide Caption 7 of 30 Photos: Anti-Trump protests after election Hundreds of Trump protesters hold a demonstration in New York's Washington Square Park on November 11. Hide Caption 8 of 30 Photos: Anti-Trump protests after election A man walks by anti-Trump graffiti in downtown Oakland, California, on November 11. Thousands of protesters have wreaked havoc on the city during anti-Trump marches, causing vandalism, fires and destruction of property. Hide Caption 9 of 30 Photos: Anti-Trump protests after election A protester kicks the window of a Bank of America branch in Portland, Oregon, on November 10. What started out as a peaceful march with more than 4,000 people quickly turned violent. Portland police publicly declared a "riot" because of "extensive criminal and dangerous behavior," according to posts on the department's Twitter page. Hide Caption 10 of 30 Photos: Anti-Trump protests after election Demonstrators flood the 101 Freeway in Los Angeles on November 10. Hide Caption 11 of 30 Photos: Anti-Trump protests after election Police officers stand guard as they slowly clear Trump protesters from the 101 Freeway in Los Angeles on November 10. Hide Caption 12 of 30 Photos: Anti-Trump protests after election Demonstrators protest in Denver on November 10. Hide Caption 13 of 30 Photos: Anti-Trump protests after election Police officers look on as someone protests in Portland on November 10. Hide Caption 14 of 30 Photos: Anti-Trump protests after election Trump protesters march toward Interstate 94 in Minneapolis on November 10. Hide Caption 15 of 30 Photos: Anti-Trump protests after election Numerous cars at a Toyota dealership were smashed as people protested in Portland on November 10. Hide Caption 16 of 30 Photos: Anti-Trump protests after election Trump protesters chant outside the White House on November 10. Hide Caption 17 of 30 Photos: Anti-Trump protests after election Protesters set an effigy of Trump on fire outside Los Angeles City Hall on Wednesday, November 9. Hide Caption 18 of 30 Photos: Anti-Trump protests after election Demonstrators march down Second Avenue in Seattle on November 9. Hide Caption 19 of 30 Photos: Anti-Trump protests after election Police respond to a fire set by anti-Trump protesters in Oakland, California, on November 9. Police said some protesters threw Molotov cocktails, rocks and fireworks at officers. Hide Caption 20 of 30 Photos: Anti-Trump protests after election Protesters in Chicago display anti-Trump signs near the Trump International Hotel and Tower on November 9. Hide Caption 21 of 30 Photos: Anti-Trump protests after election Trump protesters take to the streets in Philadelphia on November 9. Hide Caption 22 of 30 Photos: Anti-Trump protests after election Thousands march down Fifth Avenue in New York on November 9. Authorities estimated as many as 5,000 people protested Trump's victory outside Trump Tower. Hide Caption 23 of 30 Photos: Anti-Trump protests after election Protesters rally against Trump in New York's Union Square on November 9. Hide Caption 24 of 30 Photos: Anti-Trump protests after election Demonstrators march past Radio City Music Hall in New York on November 9. Hide Caption 25 of 30 Photos: Anti-Trump protests after election People listen to speakers protesting Trump's election in Seattle on November 9. Hide Caption 26 of 30 Photos: Anti-Trump protests after election A woman argues with police officers during a protest in New York on November 9. Erin Michelle Threlfall, the woman pictured, told The Huffington Post she was attempting to intervene on behalf of a man she says the police were beating. Hide Caption 27 of 30 Photos: Anti-Trump protests after election Sasha Savenko, left, and Sydney Kane join thousands of protesters in Seattle on November 9. Hide Caption 28 of 30 Photos: Anti-Trump protests after election Crowds rally outside Trump Tower in New York on November 9. Hide Caption 29 of 30 Photos: Anti-Trump protests after election Charles Watkins speaks out at an anti-Trump protest in Denver on November 9. Hide Caption 30 of 30

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.

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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."