- A look at Trump's policies to see what kind of U.S. president he'd really be
- From Mexico "Wall," to ISIS, and Israel, there is perhaps no more polarizing figure in politics
America's most unpredictable candidate could turn into America's most unpredictable commander-in-chief.
"We're not going to be the dummies anymore," he told supporters in late February. "We're going to be the smart ones."
Trump has been many things -- a billionaire real-estate developer, a brash reality-TV star and a best-selling author. But he's never held elected office or delved deeply into foreign policy.
"I don't think he's drawing on a deep reservoir of knowledge on these issues," said former American diplomat Christopher Hill.
"He comes across as someone with a lot of instincts and not a lot of reserve about acting on those instincts."
Trump vows to champion U.S. economic strength and military power -- "to make America great again," as he says.
He's giving voice to many voters' frustrations and fears about America's place in the world.
What he would do about them is sometimes less clear.
The centerpiece of Trump's presidential campaign is the plan to build a wall along the U.S. border with Mexico as a barrier against illegal migration, criminals and narcotics trafficking.
Trump insists Mexico will pay for it. A spokesman for Mexico's president says his government will not.
Whatever the ultimate source of the financing, it would almost certainly involve billions of dollars passing through the coffers of the U.S. government, which only Congress has the authority to approve.
And there has been no rush by Washington lawmakers to embrace the plan.
Trump vows to "bomb the hell" out of ISIS in Iraq -- especially the oil wells it's captured there -- to deprive it of income.
In Syria, Trump says he would leave the job of fighting ISIS to the government and -- alone among major presidential candidates -- he has welcomed Russia's military support for the regime.
Under Trump, the U.S. would also refuse to accept Syrian refugees (and, at least temporarily, all Muslims from anywhere in the world).
Instead, he proposes a safe zone for civilians inside Syria that Washington would help fund but other nations would build and defend.
War on Terror
Trump would resume the widely condemned interrogation technique known as waterboarding, adding that "it's not really tough enough."
He's told voters that "torture works" -- and he would also maintain the U.S. prison at Guantanamo Bay, Cuba, and add more prisoners.
Trump maintains that the U.S. is being exploited by its trading partners -- reserving the worst of his wrath for China.
He told the New York Times he plans to impose a crushing 45% tariff on Chinese imports. Trump later denied saying this, but the Times had taped the interview and released the recording.
In 2011, Trump urged U.S. intervention to help Libyans topple Moammar Gadhafi. Last month, he denied it. But once again, there is a recording of his original remarks.
Now a vocal critic of the U.S. invasion of Iraq in 2003, Trump couldn't explain supportive comments that he'd made about it beforehand. "That was a long time ago," he told NBC News, "and who knows what was in my head?"
Trump subsequently told CNN he changed his mind before the war began.
Trump is frustrated with the cost of the U.S. military presence in Europe and the pressure to lead NATO. "Where's Germany? Where are the countries of Europe leading? I don't mind helping them. I don't mind being right behind them," he said.
He also wants South Korea to support more of the cost of its American military protection. "We get nothing for this. I'm not saying that we're going to let anything happen to them. But they have to help us," he said. In fact, the US receives more than $800 million annually from South Korea for its troop presence, according to Politifact.com
Trump has both pledged to be "neutral" in trying to make peace between Israelis and Palestinians and also pledged his full support for the Jewish state.
If there is any consistent theme that emerges, it's grievance: America's borders are too open to foreigners, its economy too easy for them to exploit, and its military alliances too one-sided in their favor, according to Trump.
If there is any other theme, it's that Trump speaks his own mind on major international issues -- and sometimes disagrees with his own mind too.
A polarizing figure
The tough-talking tycoon is probably the most polarizing figure in American public life today -- it's no surprise that experts don't agree on what he would bring to the White House.
"Under a Trump presidency, foreign policy will be firm and proactive and similar to that of the Reagan's years -- a classic peace-through-economic-and-military strength, rather than the vacillating and dangerous weakness of the current White House," said economist Peter Navarro of the University of California.
But Jamie Metzl, a former official of the U.S. State Department and one-time Democratic candidate for Congress, said: "the world is a complex ecosystem and the level of thuggery that Don Trump has shown in this race would be extremely unsettling."
Even if he makes it to the White House, Trump would hardly have a free hand. Congress and the courts can stymie the policies of any president. Activists, industry, and myriad interest groups exert their influence. Public opinion generates its own pressures on how America navigates the planet.
Beyond his boardroom and reality TV broadcasts, Trump is largely untested.
After the startling spectacle Trump has offered America and the world these last few months, how can anyone know what to expect?