Former vice president Joe Biden has emerged as the anointed moderate to take on Senator Bernie Sanders. Despite poor performances in the Democratic debates and a fourth- and fifth-place showing in the Iowa caucus and New Hampshire primary respectively, Biden’s victories in states like Michigan, Texas, and North Carolina have made him the “unity candidate” to defeat Donald Trump. Biden, the theory goes, can best appeal to the disparate constituents seeking to oust Trump.

Yet Biden personifies the ways Democrats have been complicit in the failures to further racial and economic equality in the United States since the 1970s. Moreover, Biden’s candidacy, not just the candidate himself, reflects a problem that has plagued the Democratic Party since World War II: the party’s unwillingness to build a coalition that includes the left.

For decades, centrists in the Democratic Party have marginalized the progressive left in the service of “electability,” of appealing to a public supposedly fearful of big-government policies. This strategy is a product of Cold War anti-communism, of liberal Democrats’ aim to appeal to a “vital center,” often through red baiting and anti-communist rhetoric. Many of these tactics have carried into the post–Cold War era. For decades, the Democrats’ approach to the left has sidelined popular progressive policies, delayed or diluted reforms in Congress, created fissures within the Democratic Party, and played into the hands of Republicans.

Starting in the early years of the Cold War, Democrats sought to ostracize, if not outright purge, the left from the party. Few Democrats were more successful in this than Hubert Humphrey. The Minnesota mayor turned senator helped form the Democratic Farmer-Labor Party (DFL) in 1944 by encouraging the merger of the Democratic and Farmer-Labor parties. Created in 1918, the Farmer-Labor Party represented a coalition of socialist, progressive, and working-class interests in both state and national politics, while the Democratic Party in Minnesota was consistently outnumbered by Republicans, even during the New Deal era in the 1930s when Democrats held large majorities in Congress. Tired of having Republicans exploit the division between the two parties, Humphrey sought to unite them.

But for Humphrey unity meant eliminating leftists from Democratic ranks. Humphrey painted Farmer-Labor Party members as “communist,” arguing that radicals—whether socialist, communist, or progressive—deserved no place within the DFL. All were a threat to “true liberals, true Democrats.” In 1947, he announced, “If I have to choose between being called a Red-baiter, and being called a traitor, I’ll be a Red-baiter.” With the help of conservatives and centrists in the Democratic Party, Humphrey stacked the party with his loyalists, and by 1948, leftists in the DFL were few and far between.

Here was the irony: Humphrey ousted the left in the Democratic Party to further the cause of American progressivism. He thought getting rid of “communists” (a synecdoche for the left) would make progressivism more palatable. In this political and cultural context, Humphrey believed, liberal Democrats could build a broad coalition and make social justice for African Americans and the poor more universal.

When elected to the Senate in 1948, Humphrey had plans to end Jim Crow, enact fair housing laws, and create full employment. But with few progressive allies in Congress to help push his legislation during the 1950s, and with Southern Democrats dominating the Senate, Republicans—and members of his own party (mainly from the South)—called Humphrey a “socialist,” too. Humphrey’s attempt to end racial discrimination in the workforce spurred Georgia Democrat Dick Russell to accuse Humphrey of promoting policies that were “socialistic and communistic.” Indeed, despite his eventual close relationship with Director J. Edgar Hoover, the FBI kept tabs on Humphrey in the early Cold War, fearing “Communist Party functionaries were supporting Humphrey” in his political campaigns.

In retrospect, Cold War liberals like Humphrey—who thought purging communists was a rational decision given the widespread fears—only contributed to the Red Scare of the 1950s. They also created a blueprint for Republicans who wish to stymie social justice: Call even moderate liberals “communist.” This is what Joseph McCarthy did, and it’s what many congressional Republicans do today. McCarthy singled out, in his terms, a “small closely knit group of…Democrats” as being “the complete prisoners” of an international communist movement. The goal was to make Americans accuse “the Democratic Party of being the bedfellow of international communism.” This was the premise from which McCarthy launched his attack on both liberals and the left.

Faced with Republican charges that attempts at social justice—and Democrats themselves—were “socialist,” Humphrey and Cold War liberals doubled down on red-baiting tactics. Humphrey even called for an outright ban of the Communist Party under the 1954 Communist Control Act. Cold War liberals argued that the ban was necessary to neutralize McCarthy, but Humphrey’s move only alienated Democrats and liberals. Historian Arthur Schlesinger Jr.—who invented the term “vital center”—was aghast at Humphrey’s shortsightedness, arguing that his bill and tactics had “not eliminated Communism or McCarthyism as an issue” and instead “destroyed one of the best Democratic talking points—that is, that we have been an intelligent and responsible opposition.”

In contrast, the civil rights movement of the 1960s proved that leftists could be effective for Democrats in passing legislation for social justice. The 1964 Civil Rights Act and 1965 Voting Rights Act would not have been realized without pressure from civil rights activists and the New Left. However, in the wake of left-wing protests against the Vietnam War and George McGovern’s failed 1972 presidential campaign, purging the left—and rebranding the Democrats as a centrist party—became fashionable again. The election to Congress of “Watergate babies” (a Democratic majority inclined to favor pro-business rather than pro-union policies) in 1974 coincided with the emergence of groups such as the Coalition for the Democratic Majority, whose leadership consisted of disaffected Cold War liberals, including Humphrey, and future conservatives such as Norman Podhoretz and Paul Wolfowitz. Together they began to reclaim power from the left wing of the party.

Such phenomena allowed conservatives—or neoliberals—to dominate the Democratic leadership. Often representing wealthy, white suburban districts, these Democrats (including Biden) scaled back their social justice agenda and worked with Republicans to reduce the size of government. As former McGovern staffer turned Senator Gary Hart said after he was elected in 1974, this new class of Democrats was not a “bunch of little Hubert Humphreys”—as if Humphrey represented an era of “big government” left-wing reform.

But the left still vied for influence in the Democratic Party through the 1970s and 1980s. One of the most formidable challenges to creeping conservatism in the party during the late 1970s was led by socialist Michael Harrington and the Democratic Socialist Organizing Committee, which fought to pressure President Jimmy Carter to back full employment under the Humphrey-Hawkins bill, a national health insurance program, and a strengthened labor movement. It didn’t work. Carter, a Southern centrist, resisted. After Carter’s loss to Ronald Reagan in 1980, Reagan’s trouncing of Walter Mondale in 1984, and the election of George H.W. Bush in 1988, the specters of “electability” and party unity haunted the Democrats, paving the way for the Democratic Leadership Council and the centrist “Third Way” of the Bill Clinton years.

Biden emerges from this history: It is the one he inherited and helped create. The fear among party elites of the Sanders’s candidacy stems from a Cold War belief that leftists repel moderate voters from politics, and derail progressive goals by demanding immediate rather than gradual action on issues such as economic inequality and climate change. But a large, cross-racial, cross-class coalition has mobilized behind Sanders’s agenda of far-reaching, progressive political change. Sanders has demonstrated that it can be done, but the Democratic Party keeps resisting becoming a vehicle for progressive reform.

To escape this problem, the Democratic Party needs to escape the shadow of Cold War anti-communism, and to embrace the economic and racial justice reforms that resonate with working-class people. This might not be accomplished in 2020, and most likely not under a Democratic Party controlled by Biden, but given the power and impact of the Sanders campaign, the future looks bright.