In Washington, high-profile funerals often fall to vice presidents. “You die, I’ll fly” was how George H.W. Bush summed up the frequent funeral part of his portfolio when he was Ronald Reagan’s No. 2 in the 1980s. (Bush attributed the quip to Secretary of State James A. Baker.) But sometimes, the passing of an august figure requires words from the highest political voice in the country, a sitting or former president. President Trump did not attend Saturday’s memorial service for Sen. John McCain (R-Ariz.) at Washington National Cathedral. Nor has Trump spoken at a funeral since moving into the White...