WASHINGTON — On July 7, the presumptive Republican presidential nominee, Donald J. Trump, met privately with House Republicans near the Capitol. I was present as chief policy director of the House Republican Conference. Mr. Trump’s purpose was to persuade the representatives to unite around him, a pitch he delivered in a subdued version of his stream-of-consciousness style. A congresswoman asked him about his plans to protect Article I of the Constitution, which assigns all federal lawmaking power to Congress.

Mr. Trump interrupted her to declare his commitment to the Constitution — even to parts of it that do not exist, such as “Article XII.” Shock swept through the room as Mr. Trump confirmed one of our chief concerns about him: He lacked a basic knowledge of the Constitution.

There is still deeper cause for concern. Mr. Trump’s erroneous proclamation also suggested that he lacked even an interest in the Constitution. Worse, his campaign rhetoric had demonstrated authoritarian tendencies.

He had questioned judicial independence, threatened the freedom of the press, called for violating Muslims’ equal protection under the law, promised the use of torture and attacked Americans based on their gender, race and religion. He had also undermined critical democratic norms including peaceful debate and transitions of power, commitment to truth, freedom from foreign interference and abstention from the use of executive power for political retribution.