The Washington Post’s chief executive told the newsroom on Friday that it would not endorse a presidential candidate, breaking with decades of precedent at the newspaper. “The Washington Post will not be making an endorsement of a presidential candidate in this election,” wrote Will Lewis, The Post’s chief executive. “Nor in any future presidential election. We are returning to our roots of not endorsing presidential candidates.” The Post has endorsed presidential candidates since 1976, Mr. Lewis wrote, when it gave its stamp of approval to Jimmy Carter, who went on to win the election. Before that, it generally did not...