It’s hardly a mystery what President Trump will do in his first 100 days. He told us.

The Obamas welcomed the Trumps to the White House on Thursday. And the president-elect sat down with the outgoing commander in chief for almost 90 minutes to talk about the political transition. 

Trump said they talked about a range of things and that he looked forward to meeting with the president “many, many more times.” 

“We really discussed a lot of situations, some wonderful, some difficulties,” Trump said. He added that Obama explained “some of the great things that have been achieved,” without elaborating on what the outgoing president had to say about that.  

For his part, Obama struck a tone of cooperation, saying to Trump, “We now are going to want to do everything we can to help you succeed because if you succeed, then the country succeeds.” 

But what is the president-elect going to do after he's sworn in next January and takes his place in the Oval Office? 

“If people are imagining, either for better or worse, that Donald Trump is not going to do what he says, I think that the history of the presidency doesn’t support that,” says Evan Osnos, who’s been writing about the Trump campaign for the New Yorker. 

Political scientists have looked back at what newly elected presidents in American history have done, and Osnos says it matches up pretty closely with what those men said they would do during their campaigns. 

“They tend to keep more than two-thirds of the things that they campaign on,” Osnos says. “Once they get into office, if they don’t do the things that they said they were going to do, they’re immediately going to lose credibility with their supporters.” 

“There’s an internal pressure that takes hold between the Congress, the White House and the public that almost compels them to do the things that they ran on,” he says. 

Trump is someone who has taken different sides on many different issues and even switched political parties over the years. But in late October, Trump gave a speech in Gettysburg, Pennsylvania, and outlined his plan for the first 100 days in office. It included a lot of specifics, including canceling "every unconstitutional executive action, memorandum and order issued by President Obama" and suspending immigration from 'terror-prone regions.'" 

Americans shouldn't be surprised if Trump's first 100 days look a lot what he promised then. 

“If you talk to his advisers, as I’ve been doing over the last few months, what they’ll tell you is that it’s a mistake to assume that he’s doing this for political theater,” Osnos says. 

The Trump campaign has talked about the new president signing a whole host of executive actions — up to 25 of them — during the first few days after Inauguration Day. Osnos says they’re calling it the “First Day Project.” 

These executive orders would include Trump calling for an end to US cooperation with the Paris Agreement on climate change, suspending the Syrian refugee resettlement program and expanding on the deportation of people in the US illegally. 

Osnos says Trump might also cancel the nuclear deal with Iran and direct the Commerce Department to bring trade cases against China.

“He could do a lot,” Osnos says. “Over the last 100 years, the power of the presidency has expanded considerably.” 

There's also a common misconception about the way the American system of checks and balances works, Osnos explains. The legislative and judicial branches of government do not actually have the power to stop a chief executive from doing things.

“What the Congress and the courts have the ability to do is try to check a president, or to challenge a president, after he has done those things,” he says. 

“The president’s major advantage is that he has the first move. Once he’s done something, it’s a fait accompli, and it’s up to the other branches to try to undo it.”