Imagine for a moment that it's Jan. 21, 2017. After a chilly inauguration the day before, the parades and festivities have ended. And the new president of the United States is ready for his or her first day of work.
"What follows is my 100-day action plan to make America great again," Donald Trump told supporters in Gettysburg, Pa., last weekend. "First I will announce my intention to totally renegotiate NAFTA, one of the worst deals our country has ever made."
Trump also promised to withdraw from a proposed Asia-Pacific trade deal that's been in the works. Both those moves would be well within the new president's authority.
"As a general matter, if the president wants to withdraw from a treaty, he simply gets to do that," said Benjamin Wittes, a senior fellow at the Brookings Institution. "That's part of the powers of the office."
Trump would also have the power to deport more than 2 million criminals in the country illegally, halt immigration from parts of the world he calls "terror prone," and quickly reverse many of the initiatives undertaken by President Obama.
"If you're an administration that lives by the executive order, than you're going to die by the executive order, too," said Stephen Moore, an economic adviser to Trump. He expects Trump would act almost immediately to reverse the power plant rules at the heart of Obama's climate agenda, as well as Obama's orders governing immigration enforcement and overtime pay.
"You could literally have a stack of executive orders on Donald Trump's desk in the Oval Office that he could sign literally in his first hours of being president," Moore said. "And that would be in many cases, I think, an enormous lift to the economy."
Other parts of Trump's agenda would require support from a friendly Republican Congress. Those include Trump's massive tax cut, the repeal of Obamacare, and that big new wall along the border with Mexico.
"Don't worry about it," Trump assured supporters. "Mexico is paying for the wall. With the full understanding that Mexico will be reimbursing the United States for the full cost of such a wall."
Hillary Clinton, meanwhile, has her own road map for the first 100 days if she winds up in the White House.
"We're not going to build a giant wall," Clinton said. "We're going to build roads and bridges and tunnels and ports and airports and water systems and a new electric grid."
Clinton told supporters in Johnstown, Pa., over the summer she will also pursue immigration reform and big new investments in clean power.
"Within the first hundred days of our administration, we are going to break the gridlock in Washington and make the biggest investment in good-paying jobs since World War II," Clinton said.
Most of Clinton's plans would require congressional support. And that would test the former secretary of state's negotiating skills, since the House of Representatives at a minimum is expected to remain in Republican hands.
"She was a fairly successful legislator," recalled former Rep. Tom Davis, R-Va. "And her husband was just very good at working with a Republican Congress. She's got that in her background. But remember, the world has changed since that time."
Washington, like the rest of the country, has grown more polarized. And either Clinton or Trump will face strong political headwinds from the very first day in office.
"Remember this," Davis said. "The president, whoever it is, will come in with a high negative — probably close to 55 percent unfavorable view. That's not the traditional kind of mandate."
Even if there's no traditional "honeymoon," though, whoever sits in the Oval Office will still wield considerable power, starting with the nomination of a new Supreme Court justice.
Presidents generally try to deliver on campaign promises — and in many cases they succeed. So like them or not, voters should take these pledges seriously.
"When somebody promises to do something, you have to think about whether that's something you'd be willing to see happen," said Wittes, the Brookings Institution scholar. "Because the powers are simply too vast and too dangerous to say, 'Well, he was probably clowning around at that point or he doesn't know what he's saying.' "