Several friends and allies of Mr. Trump said that “negotiating” was the word he used the most to encapsulate his first 100 days in office. He wants to put strong-willed people — business executives and generals are mentioned most often — in charge of cabinet agencies and throughout his senior staff, and direct them to negotiate deals and plans with congressional leaders and state officials, as well as insurance companies and others in the private sector. They say he will accomplish the things he has promised or else keep trying, well aware that his supporters will have his head if he does not.

“He’s not going to depart from the agenda he’s laid out, not a bit,” said Roger Stone, a longtime adviser and confidant. Mr. Stone declined to describe details of his private conversations with Mr. Trump, except to say: “Having gone out a thousand times to say ‘I’m going to build a wall,’ he has to build a wall. He has said he would scrap trade deals; his voters will demand he scrap trade deals. He knows that.”

Modern America has never seen anything like a Trump administration. Business leaders and even entertainment figures new to politics have been elected governors, of course, and insurgents like Newt Gingrich rose to power.

But this is different. A Manhattan real estate developer and bombastic reality television star, Mr. Trump would be a president like no other. Yet historians suggest the country would adjust: He would quickly find himself consumed with the urgent and normalizing tasks of building a cabinet, assembling senior staff and reassuring Wall Street and the public that he was capable of governing America.

“Trump is predicting he’ll be able to do all these things, but his workload will be pretty enormous and his power would be so limited by precedent, by the bureaucracy, by the Constitution,” said Robert Dallek, a presidential historian. “Even in trade and immigration, where Trump says he will make revolutionary changes, Congress has a say on those things. A lot of people have a say. The president is not king.”

But Mr. Trump pledged in the interviews to deliver on his campaign promises, even if they prove disruptive or explosive.

On his first day in office, he said, he would meet with Homeland Security officials, generals, and others — he did not mention diplomats — to take steps to seal the southern border and assign more security agents along it. He would also call the heads of companies like Pfizer, the Carrier Corporation, Ford and Nabisco and warn them that their products face 35 percent tariffs because they are moving jobs out of the country. Democrats and some Republicans have warned that financial markets would react poorly and that Mr. Trump’s protectionist stances might plunge the country into recession, but he insisted that trade is “killing the country” and “the markets would be fine.”