When he started his long-shot bid for the White House in 2015, Donald Trump appeared to know as much about the Constitution as you might expect of any real estate developer slash reality show host slash beauty pageant judge.

One year after his election — and almost 10 months after he swore on a Bible to preserve, protect and defend that founding document — it’s not clear he knows much more, or aspires to.

Instead, throughout his candidacy and presidency, Mr. Trump has treated the Constitution less as a guiding light than as an inconvenient hindrance.

“His idea of the presidency is, he was elected and he can do whatever he wants,” said Corey Brettschneider, a professor of political science at Brown University and author of “The Oath and the Office: A Guide to the Constitution for Future Presidents,” which will be published in 2018.

“Presidents usually regard the oath as a set of legally binding principles that they abide by,” Mr. Brettschneider said. “Trump tends to think of things in terms of real estate law — ways to get around legal requirements rather than enforcing and promoting them. That’s scary, because we rely on a president to espouse the norms of the Constitution.”