On September 16, activists from around the country will converge on the Washington Monument to rally in support of, among other things, the embattled right to vote. They will have come 860 weary miles in six weeks—all the way from the Edmund Pettus Bridge in Selma, Alabama. That bridge, where Alabama State Police savagely beat black and white marchers in 1965, was the birthplace of the Voting Rights Act and the political revolution it sparked around the South.

This summer marks the 50th Anniversary of the VRA. In recent years, a small but determined band of conservatives have waged war on the Act in the courts. And a mere two years ago, Chief Justice John Roberts and his conservative colleagues on the Supreme Court gutted this landmark civil rights measure, eliminating a key provision that required jurisdictions with a history of discrimination to justify new voting regulations before putting them into effect. Emboldened, conservative legislators around the country have rolled out dozens of measures making it harder—particularly for minorities—to vote. Members of Congress have proposed legislation to remedy the Court’s decision—but so far, the leadership of the two Houses has refused even to give the measure a hearing.

The arrival of the “Journey for Justice” in Washington, D.C. next month will offer congressional leaders and the Supreme Court’s conservative majority a chance to consider the legacy they will leave to history, a legacy whose future can be foretold by the past in a tale of two presidents named Johnson—both of Southern heritage, both ascending to the presidency following a tragic assassination, and both stubborn men intent on enforcing their will on American politics. One Johnson would seize his moment and champion the most important piece of voting rights legislation in American history. The other would squander his opportunity and, in the process, secure his place as one of American history’s greatest villains.

Our tale begins in New Orleans. It’s July 30, 1866. For many months, President Andrew Johnson and congressional Republicans have been battling over the future of the post-Civil War South. An avowed white supremacist, Johnson has pursued a lenient path of Southern “restoration,” pardoning ex-Confederates and leaving the fate of the newly freed slaves to the Southern states. Beginning in December 1865, Congress decides to fight back.

In the ensuing months, President Johnson and congressional leaders would battle over a series of important measures, including the Freedmen’s Bureau bill, the Civil Rights Act of 1866, and the newly drafted Fourteenth Amendment. While congressional leaders decried the South’s treatment of the newly freed slaves and argued for greater federal oversight of the Southern state governments, Johnson defended his own lenient policy, insisting that things weren’t that bad for the freed slaves and arguing that Southerners were, in fact, peaceful and ready to accept the Civil War’s outcome. The New Orleans riot on July 30, 1866, would belie Johnson’s assurances.

In the months leading up to the riot, white conservatives seized control of the Louisiana state government. Alarmed, local Republicans and Unionists sought to reconvene the state’s constitutional convention and draft a new state constitution—one that would guarantee African American suffrage, disenfranchise many former rebels, and form a new state government. Conservative leaders (including the newly elected mayor of New Orleans, an ex-Confederate himself) were ready to fight back—quite literally.

On July 30, 1866, a biracial group of Louisiana reformers gathered in New Orleans—25 convention delegates and 200 African-American supporters, mostly Union veterans. What unfolded next was, to quote General Phillip Sheridan, “so unnecessary and atrocious as to compel me to say that it was murder.” Sheridan added, “It was not a riot; it was an absolute massacre.”

White Louisianans converged on the convention hall. Shortly thereafter, local police—many of them Confederate veterans—joined in the violence, firing into the building and shooting the delegates and their supporters as they fled. Early reports described a gruesome scene, with white citizens and the police “stabbing and smashing the heads of many who had already been wounded or killed.” Federal troops eventually arrived, but by then 34 African Americans and 3 white delegates were already dead and more than 100 had been injured.

The New Orleans riot was a turning point for Reconstruction politics. The violence—a response to the mere prospect of African-American suffrage and rebel disenfranchisement—confirmed the North’s worst fears, that the former rebels were unrepentant and that both the newly freed slaves and their white Unionist supporters needed federal protection.

The riot also gave President Johnson a chance to reverse course. Instead, he chose to double down. With a pivotal congressional election looming, President Johnson hit the campaign trail—an unusual move at that time by a sitting president. But rather than use his status as President to elevate the public debate, Johnson appealed to the lowest common denominator, defending his lenient approach to the South, levying vitriolic attacks against his congressional opponents, and even lashing out against hecklers in the audience. When one audience member cried out “hang Jeff Davis,” Johnson replied by suggesting a lynching for the leading Radical in the House: “Why not hang Thad Stevens? General Ulysses Grant—forced to attend these events by the sitting President—later called the entire episode “a national disgrace.”

The result?: an electoral shellacking. Republicans secured veto-proof majorities in the U.S. House and Senate. From there, Johnson and his supporters suffered a string of defeats, leading to African-American suffrage (and office-holding) in the South (at least for a time), presidential impeachment, the ratification of the Fourteenth Amendment, General Grant’s election as president, and, finally, the ratification of the Fifteenth Amendment, which promised an end to racial discrimination in voting nationwide.

Of course, it would take another century to make the Fifteenth Amendment’s promise a lived reality for many African Americans—which brings us to the second part of our tale, one that also features a group of courageous reformers, a bloody episode of racially motivated violence, and a President Johnson from the South. However, this story has an even happier ending.

It’s March 7, 1965. Frustrated by federal dithering on voting rights, leaders of the Civil Rights Movement converged on Selma, Alabama. In a scene reminiscent of the New Orleans riot, white police officers attacked the peaceful marchers on the Edmund Pettus Bridge. This “Bloody Sunday”—captured on television for a national audience—shocked the conscience of Americans of all races and regions. Rather than ignoring the violence, our second President Johnson called a special session of Congress. Seventy million Americans tuned in to hear his speech.

“As a man whose roots go deeply into Southern soil I know how agonizing racial feelings are,” Johnson said. Nevertheless, he argued that all Americans should embrace the cause of voting rights: “What happened in Selma is part of a far larger movement which reaches into every section and state of America. It is the effort of American Negroes to secure for themselves the full blessings of American life. Their cause must be our cause, too. Because it is not just Negroes, but really it’s all of us who must overcome the crippling legacy and injustice.”

Finally, adopting the rallying cry of the civil rights movement, Johnson punctuated his speech with four words: “And we shall overcome.”

Following months of legislative wrangling, President Johnson, the Civil Rights leadership, and their congressional allies secured passage of the Voting Rights Act on August 6, 1965. And with it, the federal government—and aggrieved voters—finally had the tools necessary to attack white supremacy at the ballot box. Once again, racially motivated violence—in this case, Bloody Sunday—begat political progress, this time with a President Johnson on the right side of history.

We no longer see racially motivated state-sanctioned violence on the scale of the New Orleans riot and Bloody Sunday. Over the last year, however, controversies over local policing tactics—sometimes punctuated by tragedy—have flared anew. African Americans no longer suffer from wholesale exclusion from the polls as in the days of Jim Crow, conservative state governments are busy limiting access to the ballot box—aided by the Supreme Court’s recent decision to gut the VRA in Shelby County v. Holder.

With the VRA turning 50, this generation’s leaders should look to the past and ask themselves how they’d like to be remembered—as a generation of Andrew Johnsons that shirked its constitutional duty to fight for political equality, or as the rightful heirs to Dr. King, L.B.J., and the civil rights movement, seizing this moment to continue to build “a more perfect Union.”

The choice is ours.