What did Donald Trump do today?

He lost the narrative on the "wall."

Trump tweeted nine times today about the border wall that is at the heart of his refusal to fund a quarter of the federal government. For much of his first two years in office, Trump basically abandoned his campaign promise to build a 1600-mile long physical barrier. But in recent weeks, he has suddenly decided (or decided to pretend) that it is so urgent that it takes precedence over literally anything else the government does—including paying 800,000 federal employees.

The consensus explanation for Trump's sudden renewal of interest in "the wall," as opposed to other forms of border security that actually work, is that he became frightened that a few fringe-right conservatives like Ann Coulter would turn on him. All presidents make political calculations, but for Trump there is a far greater danger in alienating his base than most presidents face. If a substantial number of Trump's strongest supporters abandon him, it could make him much more vulnerable to removal from office and post-presidency criminal prosecutions.

The latest tweetstorm came as reporting sourced to his own advisors and campaign strategists revealed that the whole idea of a "wall" was never supposed to be more than a mnemonic device. His handlers on the campaign trail felt that Trump, who even friends admit is undisciplined on his best days, needed an easy catchphrase to keep him focused. It was not intended by those handlers as an actual policy item. (Even conservative immigration hardliners don't generally think a physical, static wall will have any real effect on border crossings.)

The federal employees who actually do guard the border are being furloughed or forced to work without pay during the shutdown.

Why is this a bad thing?

• It's bad if a president is so easily manipulated that his handlers can end up creating policy by accident.

• Actual border security is more important than Trump's political or legal future.