President Donald Trump plus a Twitter account. Yeah, that'll go well.
Here's an article about Donald Trump's usage of Twitter, and how maybe being retweeter of random fever swamp nonsense right be a bad trait for an actual president of the United States to have. Put it down as part of the ongoing process of the political news world coming to terms with the notion that the next Republican nominee for the presidency is likely to be a raving half-lunatic.
Yet Trump's pattern of repeating things that are false, or just unseemly, and then refusing to take responsibility, would undoubtedly pose a challenge should he move into the White House — where a president's casual utterance or late-night tweet could move financial markets or spark a diplomatic incident.
Trump has been called out for retweeting white supremacists (multiple times), and for retweeting conspiracy theories (not surprising, considering his anti-Obama birtherism is what turned him into a conservative "star" in the first place), and for retweeting made-up statistics and made-up assertions and made-up whatever else might cross his iPhone screen, so long as it reinforces his particular message-of-the-moment. And yes, one can imagine how much of a disaster that might be if done by a sitting president. Nothing would make for a more interesting round of foreign diplomacy than having each foreign leader subjected to a Twitter-roast from President Trump and President Trump's million's of riled, racist followers.
There have been some previous pundit pieces about Donald Trump's "mastery" of Twitter; this, thankfully, is not one of those. But it bears repeating that Donald Trump is not a master of Twitter. Donald Trump uses Twitter as a child would. He retweets things that make him look good. He pours molten invective over anyone who makes him look bad. Saying Donald Trump has mastered Twitter through a nearly obsessive-compulsive combination of self-promotion and insults is like saying a preteen boy has mastered the video game Call of Duty because he knows how to use every foul word he's ever learned in each and every online match.
On the other hand, I do not think that a President Trump calling foreign leaders "stupid" or "losers" on Twitter would necessarily be the diplomatic crisis that it would be if, say, a President Anyone Else did it. Everyone knows at this point that Donald Trump is a man-child. Everyone is well familiar with his tantrums. It's very likely that all foreign diplomacy with the United States would simply stop cold, rather than deal with the crackpot in the round-walled room, as the entire world decides to take a little break and see if we might come to our senses. We probably would, eventually. We love our reality shows, here in America, but in the end we don't have very long attention spans.