Can you guess which world currency has gained the most since Donald J. Trump’s inauguration as president?

Here’s a clue.

It has something to do with a “big, beautiful wall” on America’s southern border.

Of all major currencies, the one that has strengthened the most since Jan. 20, the day Mr. Trump became president, is the Mexican peso. In his inauguration speech, Mr. Trump pledged to “bring back our jobs” and “bring back our borders,” in veiled references to Mexico. Since that day, the Mexican peso has gained more than 15 percent.

What’s startling is that the peso served throughout the presidential campaign as a proxy for Mr. Trump’s political fortunes. The connection isn’t perfect, but the two have had a very close and extremely uncomfortable relationship. And at the moment, it has taken an unexpected turn.

Recall that on the night of Mr. Trump’s stunning election victory, the peso immediately took a brutal beating, plunging 12 percent against the dollar. That move was consistent with patterns throughout the presidential campaign. Whenever Mr. Trump’s prospects rose, the peso’s dived. Whenever he raised the volume on promises to build a towering wall on the Mexican border or to stamp out “bad hombres” or to crack down on immigration, the peso lost some of its value.