Trump's UK trip shows he still doesn't know how to be a president — and he never will: Conservative columnist

President Donald Trump's trip to Europe was a massive humiliation for America, and yet another reminder that Trump is incapable of following the norms and decorum of his office, writes conservative columnist Max Boot for the Washington Post.

"At one time, it was naively assumed that, in the unlikely event that he won the presidency, Trump would tone down the lying, the bragging, the nativism and the insults, and act more, well, presidential," writes Boot. "Trump himself promised that 'with the exception of the late, great Abraham Lincoln, I can be more presidential than any president that’s ever held this office.' Another lie. We are more than halfway through Trump’s term, and his behavior remains as 'unpresidented' as ever.

Boot lists off all the major unwritten rules that Trump stomped on during his trip.

"Don't engage in domestic politics overseas — and don't engage in name-calling," writes Boot, and yet Trump called former special counsel Robert Mueller a "fool" and House Speaker Nancy Pelosi (D-CA) a "disaster" at the D-Day ceremony in Normandy. "Don't lie," writes Boot, and yet Trump lied about everything from climate change to the crowd size of the supporters and protesters in London. "Don't intrude into other democracies' politics," writes Boot, and yet Trump offered several opinions on Brexit, the leadership race for prime minister, and the National Health Service, and Irish border security. "Don't mix government business with personal business," writes Boot, but Trump visited his own golf course in Doonbeg at taxpayer expense to give the Trump Organization publicity.

All of this, Boot says, "makes me ashamed to be an American."

"From the start of his campaign in 2015 until today, Trump has been nothing if not consistent in his contempt for behavioral norms," concludes Boot. "It's not his fault that he is so awful; after 72 years, he can't help himself. It's our fault that we elected him and might reelect him in 2020."