Donald Trump has fooled many people – even Brian Mulroney

The late Brian Mulroney got to know no fewer than 10 American presidents. Donald Trump, who has just wrapped up the Republican nomination process for another run at the presidency, was one of the ones he knew best. Or so he thought. Their relationship, the late Mr. Mulroney told me in an interview last year, went back decades to when they saw each other a lot in New York. It continued in Palm Beach, Fla., where he had a residence close to Mr. Trump's Mar-a-Lago estate, which Mr. Mulroney and his family visited frequently. He and Mr. Trump were such…