Attorney General Jeff Sessions offered an indignant defense on Tuesday against what he called “an appalling and detestable lie” that he may  have colluded with the Russian effort to interfere in the 2016 election, showcasing his loyalty to President Trump in an often contentious Senate hearing but declining to answer central questions about his or the president’s conduct.

Attorney  General Jeff Sessions was scheduled to testify publicly next Tuesday  before the House and Senate appropriations committees. On Saturday, he  abruptly canceled. In  letters to the chairmen of the committees, Sessions writes that he will send his deputy, Rod Rosenstein, to the hearing instead. In explaining the cancellation, Sessions writes that he believed that members of the committees were planning on asking him about “issues related to the investigation into Russian interference with the 2016 election.”

President Trump on Friday accused James B. Comey, the fired F.B.I. director, of lying under oath to Congress, saying he would gladly provide sworn testimony disputing Mr. Comey’s charge that the president  forced him out because of his handling of the investigation into the Trump campaign’s possible collusion with Russia.

John O. Brennan, the former director of the C.I.A., offered the fullest public account yet of how the federal investigation into Russian election meddling began. In testimony before the House Intelligence Committee, Mr. Brennan described a nerve-fraying few months as American authorities realized that the election was under attack and worried that Mr. Trump’s campaign might be aiding that fight. His remarks were the fullest public account to date of the origins of an F.B.I. investigation that continues to shadow the Trump administration.

Sally Yates’s tenure as the Trump administration’s acting attorney  general was short-lived but eventful. A holdover from the Obama Justice Department, Yates didn’t make it two weeks before she was dismissed for refusing to defend Trump’s first travel ban. But before she departed, she warned White House counsel Donald McGahn that National Security Adviser Michael Flynn had misled his superiors about his preelection conversation with the Russian ambassador to the United States. Weeks later, word of that warning leaked to the press — and Flynn promptly resigned.