"A man you can bait with a tweet is not a man we can trust with nuclear weapons."

So said Democratic presidential nominee Hillary Clinton during this year's DNC, and it turns out she was being prophetic.

The Wall Street Journal reports that Donald Trump changed his speech on immigration at the last minute to include references to Mexico paying for his proposed border wall.

The reason that Trump decided to make this change? Because he was apparently furious that Mexican President Enrique Peña Nieto just posted a tweet insisting that his country would never, under any circumstances, pay for the wall.

"Mr. Trump was peeved that Mr. Peña Nieto had gone public with the fact that the Mexican president had broken what Mr. Trump considered a deal to keep the question of paying for the wall off the table at their initial meeting," the Journal writes. "So Mr. Trump hurriedly inserted a new sentence in his immigration speech... adding, 'They don’t know it yet but they’re going to pay for the wall.'"

At any rate, leaders of other countries are likely taking notes right now about just how easy it is to manipulate Trump by challenging his manhood -- it will be interesting to see how he reacts when, let's say, Vladimir Putin chides him for not having the guts to lob a nuclear missile at Iceland.