At a White House event last week, Donald Trump took a couple of minutes to express confidence about the fate of the Republican plan to overhaul the American health care system. “We’re talking about a great, great form of health care,” the president said, adding, “And we are looking at a health care that would be a fantastic tribute to our country; a health care that will take care of people, finally… This health care would be so good.”

NBC’s Seth Myers joked, “He sounds like a high-school student who didn’t read the book, or have the book, or know how to read.”

The New York Times put together a video of Trump’s public comments on health care, which show him repeatedly saying lots of words, none of which amount to much. “If your only source of information was the president,” the Times noted, you wouldn’t know almost anything about the Republican plan.

The Washington Post reported over the holiday weekend that even some White House allies “are increasingly frustrated” that the president isn’t using his platform to sell his party’s proposal.

Trump has spoken out repeatedly during his tenure about the shortcomings of Obamacare, which he brands a “disaster.” But he has made relatively little effort to detail for the public why Republican replacement plans — which fare dismally in public opinion polls — would improve on the former president’s signature initiative. The lackluster sales job, combined with recent controversial tweets and public statements targeting the media, has diminished the focus on the president’s leading legislative priority at a key juncture in the Senate, allies and analysts say.

Barry Bennett, a Republican operative who advised Trump’s campaign last year and remains close to the White House, told the Post, “It’s a mystery.”

No, it’s not.

When the Affordable Care Act was taking shape several years ago, Barack Obama was an eager salesman. He hosted town-hall meetings; he did in-depth interviews; and he spoke to a variety of organizations (including, in one instance, a congressional Republican gathering). At every opportunity, the Democratic president believed the facts were on his side, and he took a stand in support of the merits of his ideas.

Trump isn’t doing any of this, and whether it’s awkward to acknowledge this or not, we know why. Indeed, we know why because Republicans have been rather candid on the issue: when it comes to the substance of health care, the president is effectively illiterate. He’s had ample opportunity to get up to speed on the details, but he’s chosen, for whatever reason, not to bother.

If Trump were to follow Obama’s example – hosting town-hall forums, fielding detailed questions from experts – the game would be up and Trump’s ignorance would be exposed. And so, he hides as his party’s proposal becomes the least popular major-party initiative in modern times.