By Paul Waldman

On the White House lawn, President Donald Trump was peppered by reporters on Tuesday about a somewhat imaginary agreement he had supposedly signed with Mexico that resulted in the elimination of tariffs he had threatened to impose on goods coming from their country.

The response, and Trump's comical attempt to convince everyone that the agreement not only exists but is fantastic, are an apt representation of where the Trump presidency is at this moment.

Angered by a wave of skepticism about the agreement, Trump produced from his pocket a folded piece of paper that he insisted was part of the agreement, though he wouldn't let anyone actually look at it.

"This is one page of a very long and very good agreement," Trump said, then went on to describe it in a something less than convincing fashion:

"Here's your thing, you know they all say, 'Oh, he doesn't,' I just give you my word, inside here, and I would love to do it, but you will freeze action it, you will stop it, you will analyze it, every single letter you'll see, but in here is the agreement."

Sounds legit. I guess we can just take him at his word, right?

Intrepid Washington Post photographer Jabin Botsford got a shot of the paper with sunlight illuminating it to show that it did seem to resemble some sort of agreement.

Without further details, it's hard to know more. But it's plausible that this piece of paper ratifies what the Mexican foreign minister has already said publicly, which is that in 45 days, if the flow of migrants hasn't slowed to Trump's satisfaction, Mexico will sit down and discuss whether to implement more far-reaching steps.

That's an agreement to talk more, not a hard-and-fast commitment to take big additional steps, which is how Trump is presenting things.

If Trump is telling even half the truth here, it's a shock.

To me this was reminiscent of the time shortly before Trump took office when he held a press conference standing before a table filled with stacks of pristine folders, all unlabeled and filled with paper that had no tabs and looked like it had just been grabbed from a brand-new ream. "These papers are just some of the many documents I've signed turning over complete and total control to my sons," he claimed, though reporters were not allowed to look at any of the documents.

Back then it was treated as a bit of absurd stagecraft, but nonetheless, the underlying claim that he was turning over his business to his sons was generally accepted. He was going to be president, after all - how could he have time to do otherwise?

But in the 2 1/2 years since, things have changed. There is no more benefit of the doubt for the president.

Trump has lied so much and with such shamelessness - 10,796 times at last count - that the default assumption for everyone, from politicians to journalists to the public, is that when he makes some new claim, if it isn't immediately corroborated by incontrovertible evidence, more likely than not it's completely false.

This one was suspicious from the beginning. It started with what has become an identifiable pattern: Trump creates some kind of crisis by making a threat, then announces triumphantly that his demands have been met and therefore the crisis has been averted through his spectacular deal-making prowess. We quickly learn, however, that the "concessions" either don't exist, predated the crisis, or aren't nearly as dramatic as what he claims.

In this case, Trump threatened Mexico with increased tariffs if they did not stem the flow of migrants from Central America, then announced that he wouldn't be imposing them after all because of a new deal. And Mexico did agree to take some additional steps to reduce the number of asylum seekers heading to the U.S. border.

But then the New York Times reported that this deal "consists largely of actions that Mexico had already promised to take in prior discussions with the United States over the past several months."

This apparently enraged Trump, who tweeted that “We have fully signed and documented another very important part of the Immigration and Security deal with Mexico, one that the U.S. has been asking about getting for many years. It will be revealed in the not too distant future and will need a vote by Mexico’s Legislative body!”

But the Mexican government denied that that was the case, instead saying they only agreed to discuss further options at some point, which is where it appears we are now.

What matters here is that when Trump does something like this, no one believes him any longer. Democrats don't believe him, and even Republicans probably know what he's saying is baloney even if they won't say so publicly. Journalists don't believe him. And the public doesn't believe him either.

Trump has been so successful in the last three years grabbing and holding all of our attention that it's tempting to conclude that he's bewitching everyone, that every ludicrous show is convincing the public. But there's a big difference between watching him and believing him.

That skepticism may help explain the fact that despite unemployment near record lows, Trump's approval remains stuck at around 42 percent. Democratic candidates regularly thump him in general election polls.

His base may exist in a blissful state of denial where everything Trump says is true and everything anyone else says is fake news, but outside of those committed supporters, he isn't fooling anyone. No matter how many pieces of paper he waves around.

Paul Waldman is an opinion writer for the Plum Line blog.

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