By now, you're almost certainly aware that Donald Trump loves to tweet.
The problem with his love of social media is that whatever the platform, when the American president speaks, the whole world listens, which is why it's not such a great idea for the leader of the free world to blurt out every random-ass notion that pops into his head 140 characters at a time.
Trump has yet to be sworn into office, and already he's provoked China, publicly pondered the idea of stripping flag burners of their constitutional rights as Americans, and gone on bizarre tirades about bad restaurant reviews.
That last one may not sound too troubling, but it doesn't provide us with much hope of seeing the "presidential temperament" Trump promised any time in our lifetimes.
(Trump's rants against corporations he's singled out might also constitute criminal stock market manipulation, but that's a discussion for another time.)
The president-elect's latest target is a member of the very exclusive fraternity that Trump himself is about to join former president Bill Clinton.
It seems the man who came so close to being our very first "first gentlemen" recently discussed the election with some residents of his Chappaqua, New York while doing some holiday shopping.
The episode was recounted by Ed Baum, editor of the small town's newspaper, who noted that Clinton was refreshingly frank in his assessment of Trump and the unexpected outcome of the vote.
Without quoting Clinton, Baum noted that the ex-president stated that he "received a phone call from the president-elect the day after the election” and that Trump was cordial throughout their conversation.
Baum says a man in the crowd then asked Clinton if Trump is "smart," to which Clinton reportedly replied:
“He doesn’t know much. One thing he does know is how to get angry, white men to vote for him.”
Not surprisingly, this response set Trump off ... bigly:
“Bill Clinton stated that I called him after the election. Wrong," Trump tweeted earlier this week.
He went on to turn Clinton's words against him, adding:
"He called me (with a very nice congratulations). He 'doesn't know much' ... especially how to get people, even with an unlimited budget, out to vote in the vital swing states ( and more). They focused on wrong states."
Obviously, there's nothing new about a Twitter attack from Trump targeting an unsuspecting victim, but this one is especially troubling, as it constitutes Trump flouting yet another unwritten rule.
Historically, presidents have been unfailingly cordial to one another, even when they don't see eye-to-eye ideologically.
By going on the offensive, Trump is lending credence to one of his critics' worst fears:
That despite having won the election, Trump will never be presidential.