Three years ago this week, Donald Trump swore an oath that he would “faithfully execute the Office of President of the United States, and…to the best of my Ability, preserve, protect and defend the Constitution of the United States.” That should have counted for something.

It did not.

What has counted for Trump—what still counts for him—is not the oath he swore but something he said a year before that, on January 23, 2016, on a swing through Iowa, when the Republican nominee tried to explain the enthusiasm of his swelling base of supporters.

“You know what else they say about my people? The polls, they say I have the most loyal people,” he said. “Did you ever see that? Where I could stand in the middle of Fifth Avenue and shoot somebody and I wouldn’t lose any voters, okay? It’s like incredible.”

The message was blunt. Trump counted on the loyalty of his partisan supporters to see him through that year’s caucuses and primaries. While he might not win everything, he would defeat abler and more experienced Republicans and secure his new party’s nomination. That made him a candidate without boundaries. When he claimed the presidency, he was determined to operate as a president without bounds.

Now, as he faces a Senate impeachment trial. Trump is sticking to his chosen course. He casually rejects the basic premises of a Constitution that few believe he has bothered to read—and that no one seriously suggests he understands. This willful rejection of his oath of office was made agonizingly clear on Wednesday, just hours after Senate Republicans blocked efforts by Democratic impeachment managers to call witnesses to Trump’s wrongdoing and to provide a full accounting of the evidence against the president.

Mocking his inquisitors from afar, Trump announced at a press conference in Davos, Switzerland, that his administration had successfully withheld materials that were required to weigh the question of whether he should be removed from office. “We’re doing very well. I got to watch enough,” Trump said of the Senate trial as it had begun to unfold. “I thought our team did a very good job, but honestly, we have all the material. They don’t have the material.”

That obvious reference to the refusal of his administration to cooperate with requests for documents regarding the impeachment inquiry was an open admission by the president that he was subverting the system of checks and balances as outlined in the Constitution. House Intelligence Committee Chairman Adam Schiff, the California Democrat who has emerged as the lead impeachment manager, pointed out Wednesday that the president had just “bragged that he thought things were going well because they had all the materials. Well, indeed they do have the material—hidden from the American people. That is nothing to brag about.”

Representative Val Demings, a Florida Democrat who serves on the House Intelligence and Judiciary committees and is also an impeachment manager, was blunter. “The second article of impeachment was for obstruction of Congress: covering up witnesses and documents from the American people,” she declared. “This morning the President not only confessed to it, he bragged about it.”

Trump is aggressively rejecting the basic premise of American governance: that separate branches of government exist for the purpose of preventing abuses of power. By refusing to cooperate with the impeachment inquiry, the president is obviously engaging in obstruction of Congress. By bragging about this refusal to cooperate, however, he is doing something more. He is effectively shooting the Constitution in the middle of Pennsylvania Avenue.

Trump is again presuming that his “most loyal voters”—this time in the Senate Republican Caucus—will stick with him. He is so confident that he is boasting about his stark abuses of power. He is betting that he will emerge unscathed even after Schiff, in a remarkable Wednesday afternoon presentation to the Senate, recalled Alexander Hamilton’s prescient warning about the danger of an American leader “unprincipled in his private life” and “despotic in ordinary demeanor.”

On Wednesday, Schiff explained how Trump had abused his position in pressuring Ukraine to open an inquiry into a political rival, and the representative told the Senate, “When the president’s scheme was exposed and the House of Representatives properly performed its constitutional responsibility to investigate the matter, President Trump used the same unrivaled authority at his disposal as commander-in-chief to coverup his wrongdoing.” Schiff described the ways in which the president “in unprecedented fashion, ordered the entire executive branch of the United States of America to categorically refuse and completely obstruct the House’s impeachment investigation.”

“In obstructing the investigation into his own wrongdoing, the president has shown that he believes he is above the law, and scornful of restraint,” said Schiff, who argued that

Such a wholesale obstruction of congressional impeachment has never before occurred in our democracy, and it represents one of the most blatant efforts at a coverup in history. If not remedied by his conviction in the Senate and removal from office, President Trump’s abuse of his office and obstruction of Congress will permanently alter the balance of power among the branches of government—inviting future presidents to operate as if they are also beyond the reach of accountability, congressional oversight and the law.

This is what is at stake. The managers of this impeachment trial have outlined the threat. But is was Donald Trump who confirmed it on Wednesday, with an admission that he is the prime conspirator in a project to obstruct the Congress that, as Adam Schiff necessarily and appropriately warned on Wednesday, “strikes at the heart of our Constitution.”