MIAMI--In an effort to steady his presidential campaign, former Vice President Joe Biden engaged in some furious damage control on Friday, a day after rival candidate Kamala Harris hurt him in the most dramatic clash so far of the 2020 election campaign.

  Addressing an African-American advocacy group in Chicago, Biden defended his record, saying he had a "lifetime commitment to civil rights". At the Democratic debate in Miami on Thursday, Harris, a black U.S. senator from California, tore into Biden for opposing mandatory school busing in the 1970s and for his cooperation with segregationists while he was a young senator.
  Biden's defensive and sometimes faltering response was viewed as a blow to his status as the Democratic race's front-runner. He has consistently held a significant lead in public opinion polls since he entered the race in April.
  The contentious back-and-forth also appeared to give Harris a boost when her campaign badly needed it, resulting in a crush of media attention, a fundraising surge, and a bevy of new endorsements.
  On Friday, Biden spoke to the Rainbow/PUSH Coalition, the African-American advocacy group founded by the Reverend Jesse Jackson, in Chicago. Before reading his prepared remarks, Biden told the crowd the debate format was insufficient for him to detail his decades-long work to promote racial equality, first as a U.S. senator and then as vice president to Barack Obama, the nation's first black president.
  “We all know that 30 seconds to 60 seconds on a campaign debate exchange can’t do justice to a lifetime commitment to civil rights,” Biden said.
  Biden was introduced by Jackson, the longtime civil-rights leader and former presidential candidate, who said Biden has “the stuff it takes to make America better.”
  During his remarks, Biden turned to Jackson and said, “I know and you know I fought my heart out to ensure that civil rights, and voting rights, equal rights are enforced everywhere.”
  Biden disputed Harris’ contention that he opposed busing, the controversial practice of transporting students to schools within or outside their school districts as a remedy for discrimination, in the 1970s, saying that he supported voluntary efforts for school districts to desegregate. He reaffirmed his support for the federal government’s power to address civil-rights abuses, and talked up Obama's accomplishments on criminal-justice reform, arguing that many of them have been overlooked.
  "I’m tired of hearing about what he didn't do," Biden told the crowd. "This man had a backbone like a ramrod."