A big part of what has gotten Donald J. Trump into so much trouble during the past few days has been his own big mouth and penchant for braggadocio.

He boasted many times while winning his campaign for the presidency that he would cut the “best” deals ever. He would renegotiate international trade deals; he would persuade companies to bring jobs back to this country; he would force Mexico to pay for “the wall” across our countries’ shared border … oh, and he would “repeal and replace” Obamacare on “Day One” of his presidency.

What about that last thing, repealing the Affordable Care Act and replacing it with something better?

He didn’t deliver the goods. Not only did he not make good on that grand campaign promise, he revealed himself to be a fraud, a sucker.

None of this would matter nearly as much were it not for the undeniable fact that Trump bragged so openly — repeatedly and loudly — about how he would transfer his legendary business acumen into running a multitrillion-dollar government operation.

No president can force other politicians to do his bidding. No president can perform a single-handed midcourse correction of the federal government.

He told us at the Republican National Convention that “I, alone” can fix the things that need fixing. Mr. President, good governance — something that is foreign to you — inherently is a team sport. It requires a partnership between two of the three branches of government: the executive and legislative branches. That’s how the founders set it up and that’s how it is intended to function. What’s more, if either of those two branches screw it up, we have the third branch of government — the federal court system — to determine whether they violate the U.S. Constitution.

Can the 70-year-old president who prior to taking office had zero direct experience with government change his ways? Can this guy ever learn how to govern?

I refer to a part of Maureen Dowd’s brilliant column in today’s New York Times. She refers to how Trump likens his ascent to power to when Ronald Reagan became president in 1981. There is an essential difference between the 45th president and President Reagan.

It is that Ronald Reagan “knew what he didn’t know.” So he sought to hire the best minds he could find to teach him. Donald Trump has yet to acknowledge that he knows nothing about the job he now occupies.

Deal maker? Big-time negotiator? The president is a fake.