What did Donald Trump do today?

He tried to pretend that a Democratic congressman supported his plan to use emergency powers to build his wall.

With public opinion against his oft-promised, ever-changing, never-built border wall, Trump needs all the allies he can get. But many of the people he claims agree with him on the wall aren't identified, like the "many" unpaid government workers Trump claims are secretly communicating their support. Others, like every living ex-president, have quickly refuted Trump's claims that they privately agree with him about border walls.

Trump tried again today in a tweet claiming that Rep. Adam Smith (D-WA) agreed that he could use a state of emergency to force the building of a wall without a Congress appropriating money to pay for it. It's true that Rep. Smith said that Trump could declare a state of emergency. This is not exactly controversial: there has been at least one state of emergency in existence at the federal level at all times for the last four decades, and there may be dozens active at any given time.

But Smith's point was that Trump did not have the legal authority to use the powers granted to presidents under the National Emergencies Act to have the military build a border wall, and that he would lose a court challenge if he tried.

ABC NEWS: Let's get right to it, does President Trump have the ability, have the authority, to declare a national emergency, have the military build his wall? 

REP. SMITH: Well, unfortunately, the short answer is yes. There is a provision in law that says the president can declare an emergency. It's been done a number of times. But primarily it's been done to build facilities in Afghanistan and Iraq. 

In this case, I think the president would be wide open to a court challenge saying, where is the emergency? You have to establish that in order to do this. But beyond that, this would be a terrible use of Department of Defense dollars. The president spends most of his time talking about how we're not spending enough on national security, now he wants to take $20 billion out of the defense budget to build a wall, which by the way is not going to improve our border security. The president seems unaware of this, but we have actually already built a wall across much of the border, and all border security experts that I talk to say, where a wall makes sense, it's already been built.

Why should I care about this?

• States of emergency don't give presidents the power to reshape reality.

• Presidents whose policies are legal and/or popular don't need to lie about people supporting them.

• Declaring emergencies and using that as an excuse to ignore laws is what authoritarians do.