Over two nights of Democratic debates last week, one defining moment stood out: the exchange between Sen. Kamala D. Harris (Calif.) and former vice president Joe Biden on racism and desegregation. Harris’s emotional reminder that she was “bused” as a little girl to desegregate public schools in Berkeley, Calif., put Biden’s previous boast about his ability to compromise with segregationist politicians in stark context. Biden, in turn, defended his remarks and touted his own record on civil rights.

But the debate over how Biden should be judged for working with segregationist Democrats such as James O. Eastland and Herman Talmadge during his early years in the Senate misses the part of Biden’s record in the 1970s that is most relevant to today. Biden was not just reaching across ideological divisions and working with conservative members of his party to, as he says, “Get things done.” Instead, Biden was part of a new breed of moderate Democrats who swept into office during the 1970s and pulled their party to the right — with major consequences still being felt today.

Biden entered elected office at a moment when the Democratic Party had just emerged as a definitively liberal party. Beginning in the late 19th century, Democrats moved from the party of white supremacy to the party of progressive reformers, organized labor, New Deal liberalism and civil rights, remaking political history in the process.

Yet, while the national platform had become solidly liberal by the 1970s, the party itself remained ideologically diverse. That meant the Democratic Party was also still the party of segregationists such as Eastland and Talmadge. This explained why in some of the biggest legislative battles of the mid-20th century — especially on civil rights and the expansion of the welfare state — intraparty politics were often more important than battles between Democrats and Republicans.

During President Lyndon Johnson’s first few years in office, as the Great Society was becoming a reality, liberals won more often than not, passing the Civil Rights Act of 1964, the Voting Rights Act of 1965, Medicare, Head Start and other progressive reforms. Politically, thanks to the popularity of the New Deal, liberalism had been an asset for Franklin Roosevelt, Harry Truman, John F. Kennedy and Johnson. But, Richard Nixon’s victory in 1968, coupled with the urban uprisings of the 1960s and Vietnam, put liberal Democrats on the defensive.

After George McGovern, perceived to have run as a far-left candidate, got drubbed by Nixon in 1972, the more moderate elements of the Democratic Party made a move for control of the party.

Those moderates didn’t embrace Southern segregationists, but they did shift the party away from the progressive policies of the New Deal and Great Society. They could do so because they were the very core of the party, from conservative big-city mayors such as Philadelphia’s Frank Rizzo to newly elected moderate senators such as Biden and Colorado’s Gary Hart. No one emblematized this change more than President Jimmy Carter, the only Democrat to win the White House between 1969 and 1993.

It is perhaps easy to confuse Carter’s post-presidential humanitarianism with his time in office. But as president, he was no progressive. Nor was he an outlier. His presidency was a direct result of the shift in the party. Two years before Carter captured the White House, Hart and his fellow “Watergate babies” — the massive freshman Democratic class who got elected as a reaction to Watergate — swept into office. They set about moving their party away from Johnson’s Great Society by advocating centrist policies, distancing the party from labor unions and making appeals to the white, suburban middle class.

Carter was not an official Watergate baby, but his candidacy capitalized on the politics they initiated. He ran for president as an outsider, the first candidate to do so successfully in the modern era. He openly rejected “ideology,” meaning he refused to identify himself as a liberal the way every Democratic president since the 1930s had done. Once in office, Carter championed the kinds of conservative reforms many people assume began under Ronald Reagan.

With the economy still reeling from the oil crisis of 1973 and the onset of stagflation, Carter didn’t offer up New Deal-style government programs to help Americans through tough times. Instead, he embraced the politics of austerity. He sought to rein in inflation by proposing dramatic cuts in government spending. He proposed cuts to social programs and reduced the size of the government workforce. He also turned toward free-market solutions to economic problems, initiating a wave of deregulation.

This move away from regulation represented a sharp break with Democratic economic policies dating back to Woodrow Wilson. Sounding like a conservative when announcing the deregulation of the airline industry in 1977, Carter declared his administration’s goal was “to free the American people from the burden of overregulation.” Carter’s austerity and deregulation were a sign of a broader shift in Democratic economic thinking.

But it wasn’t only on economic issues that Democratic politicians turned to the right. Similar shifts also occurred on more divisive social issues. Biden’s much-talked-about opposition to “busing” provides a case in point.

Biden was only one of thousands of Democrats who opposed federally mandated “busing,” a catchall term that had been used to add a colorblind veneer to a range of efforts to stop school desegregation since Brown v. Board of Education. By the 1970s, opposition to “busing” was strongest in Democratic strongholds, cities such as Philadelphia, Chicago, New York and Baltimore — as well as Biden’s own Delaware.

Sensing their political weakness with what would become known as “Reagan Democrats,” moderates such as Biden, Hart and Carter worked to move the party decidedly to the right of where it had been for decades. These efforts represented nothing less than an effort to reimagine the Democratic Party, to abandon the politics of the New Deal and Great Society in favor of privatization efforts to achieve priorities such as health care for all and a smaller federal government.

This push prompted Ted Kennedy’s unsuccessful primary challenge to Carter in 1980, which split the party and paved the way for an era of Republican presidents. This Democratic drift to the right in the 1970s is often overlooked in our political history, but it was every bit as important in ushering in an era of conservative dominance as the rise of the Republican right. Not only did it split the Democrats, but it also left them without a true vision to counter Reagan’s conservatism.

Biden was part of that change in Democratic politics. This is the element of his early record that ought to be understood today. Biden was no segregationist, nor was he a conservative like Eastland. Nonetheless, he did contribute to moving the party to the right in a way that had major policy ramifications on issues ranging from school desegregation to the growing wealth gap.

Today, the Democratic Party is once again at a crossroads. The party’s resurgent liberal and left wings are rightfully skeptical of the compromises Biden made in the past. If he hopes to appeal to these Democrats or campaign on his record on civil rights, he also needs to reckon with the effects of the compromises he made early in his career, and the ways he and leaders such as Hart and Carter remade the party in the 1970s.