Trump gave a little more context in an interview clip posted by the Fox News program "Fox & Friends," which showed Trump trying out the line in response to a reporter remarking that the world was changing.
"We saw Brexit, and now we're seeing this in the United States," the reporter said, not really asking a question.
"Well I think I will be called Mr. Brexit," Trump responded. End of clip.
Did Donald Trump really tweet that?
The metadata on the tweet says it came from an Android Twitter client, which analyses have shown are the ones Trump likely writes himself. This idea was likely a 100% Trump original. (Sorry, a 100% MR. BREXIT! original.)
What does Trump mean by "MR. BREXIT!"?
Good question. "Brexit" is a portmanteau of "Britain" and "exit" and was used by politicians and the press to describe a referendum vote in the United Kingdom earlier this summer to leave the European Union.
What does Donald Trump know about Brexit?
"And Brexit? Your position?"
"The Brits leaving the EU."
"Oh yeah, I think they should leave."
Sometime between then and the day after the vote, Trump brushed up on the topic enough to opine about it on his Twitter account during a trip to Scotland for the reopening of the Trump Turnberry golf course.
He doubled down on his Brexit support later on at his golf course, and tied the UK's vote to leave the EU to his "Make America Great Again" campaign.
"People are angry all over the world. They're angry over borders, they're angry over people coming into the country and taking over and nobody even knows who they are," Trump said. "They're angry about many, many things in the UK, the US and many other places. This will not be the last."
So when Trump says people will soon call him MR. BREXIT!, what does it mean?
In the Fox News clip, Trump is mostly referring to general anti-establishment political fervor of the kind that has powered his campaign. But he could also be referring to polls.
British polls were divided going into June on whether the UK would vote to leave the EU or not, but many predicted that the Remain side would win in the days leading upto the referendum. Betting markets were even more certain. And when the Leave side ended up victorious, 51.9 to 48.1 percent, it shocked Brits who had trusted the polls.
Trump probably sees his own campaign following a similar path across the finish line. Recently, the Trump campaign has gotten anxious over polls showing Hillary Clinton breaking away with a lead in a majority of swing states. A Brexit-style shock upset is still an outcome Trump and his surrogates can hope for, even as their poll numbers fall. And hope is something his campaign desperately needs right now.
So…is that it?
I mean this is Donald Trump we're talking about here. More than any other politician in recent memory, he has embraced that idea that any publicity is good publicity. By firing off this weird, context-less tweet into the ether on a Thursday morning, he's gotten everyone talking.