Should "President of Mexico" Be Capitalized? Yes—It's a Proper Title

Yes. "President of Mexico" is a proper noun phrase—a formal title referring to a specific office—so it follows standard capitalization rules:

• Capitalize each major word: President of Mexico
• Same as: President Biden, Queen Elizabeth II, Prime Minister of Canada, Chief Justice of the Supreme Court

When Not to Capitalize

Use lowercase when referring to the role generically:

• "The president of Mexico serves a six-year term."
• "She wants to become president of Mexico someday."

Rule of thumb: Capitalize when used as a title before a name or as a formal office name; lowercase when used descriptively.