WASHINGTON — Since the founding of our republic, there have been precisely 1,974 members of the United States Senate. John McCain is only the eighth senator who was not also president or vice president to lie in state in the rotunda of the Capitol — and only the 31st individual overall to be so honored in American history. Yet, for the first time in recent memory, a sitting president of the United States did not participate in the funeral or other ceremonies honoring that individual — because the president made himself unwelcome by his behavior.

As recently as Aug. 21, just days before McCain’s death, President Trump attacked him at a West Virginia campaign rally, declaring, “We had [Obamacare] beaten, but one man — I’m sure nobody knows who I’m talking about — voted no, shockingly.” He launched similar attacks at rallies this summer in Tennessee, Nevada, South Carolina, Minnesota and New York. At last month’s signing ceremony for the John S. McCain National Defense Authorization Act (the last bill passed by the McCain-led Senate Armed Services Committee) Trump declined to even utter McCain’s name, leaving it off the bill name in his remarks. When a White House aide declared McCain’s opposition to Gina Haspel’s nomination as CIA director “doesn’t matter” because “he’s dying anyway,” Trump did not permit press secretary Sarah Huckabee Sanders to apologize. And last week, after McCain died, the White House raised its flags from half- to full-staff on Monday, until it came under pressure from veterans’ groups to lower them again. When asked at press gaggles to comment on McCain’s passing, Trump stared ahead in silence, unable or unwilling to muster a kind or generous word.

Add to that the fact that, to this day, the president has still never apologized for his declaration that McCain was “not a war hero” because “I like people who weren’t captured” — a comment that was deeply offensive not just to McCain but also to all American prisoners of war — and it is little wonder the McCain family wanted the president nowhere near his flag-draped casket.

Trump didn’t like McCain, in some cases with good reason. But when you are president, you sometimes have to honor people you didn’t like or who didn’t like you. You have to put aside personal and political differences and represent not yourself but the office you occupy and the country you lead. Trump seems to be congenitally incapable of rising to such occasions — even when it is in the national interest and his own interest to do so.

Sen. Lindsey O. Graham, McCain’s closest friend in the Senate and a Trump supporter, says he’s told the president “several times” that his attacks on McCain were “beneath the office,” adding, “I don’t see how it helps the president.” To the contrary, those attacks hurt Trump. It’s one of the reasons that — despite a booming economy, historically low unemployment and American factories hiring at their fastest rate in decades — a new Washington Post/ABC News poll found that 60 percent of Americans disapprove of the job Trump is doing, including 31 percent of self-described conservatives. Trump should be riding high in the polls, winning over skeptics with economic successes. Instead, he is managing to raise both the gross domestic product and his own disapproval at the same time.

No doubt Democrats took advantage of McCain’s passing to cast Trump in a negative light. Their praise for McCain was, in many cases, opportunistic. When he was running for president in 2008, they attacked him brutally. But their hypocrisy does not justify Trump’s gracelessness.

As the Senate begins hearings this week on Trump’s nomination of Brett M. Kavanaugh to replace Justice Anthony M. Kennedy on the Supreme Court, conservatives are reminded how important it is that he, and not Hillary Clinton, is sitting in the Oval Office. But this past week has also served as a reminder that good policies do not excuse abhorrent behavior. If Trump cannot muster the wherewithal to be presidential when the occasion demands it, he may end up being a successful president — but he will never be a great president.

Marc Thiessen is a columnist with The Washington Post. Follow him on Twitter, @marcthiessen.

Marc Thiessen