Supporters hold signs at a Donald Trump rally held in early May in Omaha. (Lane Hickenbottom/Reuters)

Senate Majority Leader Mitch McConnell recently worried publicly that Donald Trump’s attacks on Latinos could damage the Republican Party, saying that when the 1964 presidential nominee, Sen. Barry Goldwater, voted against the Civil Rights Act, it “did define our party, for at least African American voters, and it still does today. That was a complete shift that occurred that year, and we’ve never been able to get them back.”

That’s often the story told about the civil rights realignment: National party leaders set off a dramatic reshuffling of coalitions. In this story, Lyndon Johnson’s aggressive push for the Civil Rights Act of 1964 redefined the Democrats as the party of racial liberalism, at least comparatively speaking, while Goldwater’s opposition turned the GOP into the party of racial conservatism. These changes reverberated down through the party system, as activists and voters followed their leaders’ cues.

But that’s backwards.

In “Racial Realignment: The Transformation of American Liberalism, 1932-1965,” I argue that top Democratic and Republican leaders were actually among the last to shift. Johnson’s civil rights stance acknowledged how Democratic activists and voters had already changed his party over the preceding 30 years. Goldwater’s alliance with Southern racial conservatives could happen only because the mass and mid-level of his party had already shifted in that direction. This has important implications for how we understand Trump’s influence on the future of the GOP.

First, the New Deal attracted African American voters.

When the New Deal was launched in 1933, most Democrats did not view civil rights as part of the liberal program. The most radical New Dealers sought to transform America’s political economy by taking on corporate power, not Jim Crow. When white liberals attacked President Franklin D. Roosevelt for his timidity, they pointed to his failures to back organized labor, to rein in business power and to fund recovery efforts — and said nothing about how he avoided civil rights.

But while parts of the New Deal perpetuated racial discrimination — leaving farmworkers and domestics out of Social Security, for instance, which meant most Southern blacks fell through the safety net — Roosevelt’s program offered real benefits to many Northern African Americans, from WPA jobs to labor protections. As a result, those Northern African Americans voted decisively for Roosevelt in 1936 and stuck with the president for the rest of his time in office. That new voting bloc motivated at least some Democratic politicians to support civil rights.

The labor movement started championing civil rights.

At the same time, the meteoric rise of the Congress of Industrial Organizations (CIO) changed the labor movement and gave African Americans an important ally within the Democratic coalition. Before the CIO was formed in 1935, the American Federation of Labor (AFL) dominated the labor movement and often excluded African Americans from good jobs and union membership. But from early on, the CIO leadership stood out among white-led organizations in supporting civil rights, despite the racial biases of many of its rank-and-file union workers.

The CIO’s civil rights support was both ideological and highly practical. Ideologically, many of the CIO’s leaders and organizers came from left-wing political movements — including communism and socialism — that believed racial divisions undermined the class consciousness required to fight economic exploitation. Practically, these union officials wanted African Americans with them so that they weren’t potential replacement workers to bust the union. Within the Democratic coalition, the CIO argued for using governmental power to tackle the mutually reinforcing problems of economic and racial inequality.

Southern Democrats reacted fiercely.

That sparked a furious reaction among Southern Democrats, who had been critical backers for the early New Deal. Southern politicians saw that bringing African Americans into both the Democratic Party and the labor movement was an existential threat to Jim Crow. And so Southern Democrats were soon cooperating with Republicans to attack organized labor, the expansion of the New Deal and the liberal agenda more generally.

Southern Democrats’ fierce opposition to that pairing — to the CIO and to civil rights — meant that African Americans weren’t isolated anymore. Their political enemies were increasingly seen as enemies of liberal advances generally, on civil rights, on labor policy and in other areas as well.

Supporting civil rights became central to a liberal identity.

Even ordinary voters backed this new alignment between racial and economic justice early on. By the early 1940s, economically liberal white Northern Democratic voters were much more likely to back civil rights initiatives than were economically conservative Republicans. African American movement activists worked hard to tighten these connections as the U.S. mobilized for World War II, pushing Fair Employment Practices legislation that barred discrimination in hiring, which soon became a core element of the “liberal program.” These efforts fostered a new understanding of “liberalism,” with support for civil rights as a key marker of a liberal identity.

Northern state parties and rank-and-file members of Congress responded to these new dynamics long before national party elites. By analyzing several hundred state party platforms from the 1920s to the 1960s, I found that by the mid-1940s, Northern state Democratic parties were far more likely to support civil rights than their Republican counterparts. Pro-civil rights platforms were more likely in states with large numbers of African Americans, Jews, union members and city residents. That showed up in the House of Representatives, where by 1945, Northern Democrats supported civil rights substantially more than did Republicans.

In sum, among Northern state parties and rank-and-file members of Congress, the racial realignment was largely completed in the 1940s.

National Democratic leaders resisted the shift as long as they could.

But liberals still had to overcome the resistance of national leaders, who had long fought the pressure to take a clear stand on civil rights, which they understood would split the party. From 1944 to 1956, rank-and-file Northern Democratic activists and convention delegates favored a more liberal stance on civil rights than did national leaders, but, with the exception of 1948, national elites managed to prevent either platform language endorsing civil rights or a nominee for president whom white Southerners would reject.

Civil rights movement activists, acting with other members of the liberal coalition, worked to force the issue to the fore. Eventually, leaders had no choice but to take sides. By that time, the liberals enjoyed a clear majority within the Democratic Party; Southern conservatives had been reduced to an isolated minority.

The Republican Party changed in ways that mirrored what was happening among Democrats.

Among Republicans, ambitious politicians on the right understood by the late 1930s that Southern disillusionment with the New Deal created an opening to unite economic and racial conservatives by appealing to “states’ rights.” But the party’s more moderate national leaders, who drew their greatest support from the Northeast, had reservations about cooperating explicitly with Southern conservatives.

In a mirror image of what was happening in the Democratic Party, below the top leadership, party activists were gradually pushing the party’s attitudes and membership toward racial conservatives during the 1940s and 1950s.

Northern Republicans in Congress, facing little pressure from their constituents to back racial equality, drifted further from their earlier advocacy of civil rights legislation, and even allied with Southerners in fighting strong Fair Employment Practices legislation in the 1940s. At the state level, President Dwight D. Eisenhower’s party-building efforts in the South, which aimed to create a suburban, moderate organization in his image, ironically created a new power base for his conservative rivals within the party.

The Goldwater movement was rooted deeply in these party shifts, which enabled racial conservatives to gain the upper hand and bring disaffected Southern Democrats into the GOP.

By the 1960s, the civil rights movement’s bottom-up efforts had forced national elites to pick sides.

In other words, the civil rights movement — and the white racist reaction to its advances — forced national elites to choose sides in the 1960s. But the mass and mid-level members of the major parties had already shifted those leaders’ bases of power. Rather than a shift starting in Washington and diffusing out and down, state parties and ordinary members of Congress forged the path that allowed pro-civil rights forces to capture the Democratic Party from below and the Goldwater movement to take hold of the national GOP.

What does this mean for Trump and the Republican Party?

The big question facing the GOP today is whether Trump’s nomination is an anomaly or, alternatively, reflects a new power balance within the party. Trump’s appeals to nativism and racial resentment clearly tap into a deep current of mass opinion among GOP primary voters.

But Trump’s situation differs from Goldwater’s in some key ways. A cadre of activists and groups deeply tied to the GOP and with extensive influence in numerous state party organizations used Goldwater to forge a conservative governing majority, at least within the party. Trump doesn’t have those kinds of ties to Republicans’ mid-level party organization.

Goldwater’s movement survived his devastating election defeat because it represented the views of ordinary Republican voters and was strongly tied to the mid-level institutional GOP. Trump certainly appeals to (many) Republican voters. But translating his appeal into changes at the party’s mid-levels may require institution-building, and that is not the strong suit of the famously individualistic Donald Trump.

Eric Schickler is the Jeffrey & Ashley McDermott Professor of Political Science at the University of California, Berkeley, and author most recently of “Racial Realignment: The Transformation of American Liberalism, 1932-1965.”