Thousands of demonstrators have converged on the United States capital of Washington, DC, to warn of threats to voting rights ahead of November’s midterm elections.

Friday’s event marked the 63rd anniversary of the March on Washington, an historic 1963 protest that galvanised the US civil rights movement.

But this year’s march had a theme that gestured to the midterms: “Defend the vote.” Civil rights leaders spoke of troubling trends that they feared would erode the voting power of Black and minority citizens.

“We know in this fight we’re fighting powerful forces, but this is why we rally today,” said Marc Morial, president and CEO of the National Urban League, a civil rights organisation.

“This is why we seek to bring Americans together of goodwill from all races, from all sections of the country, to push back as forcefully as we can.”

Since taking office for a second term, President Donald Trump has undertaken efforts to restrict voting that critics fear will limit access for lower-income and minority voters.

That includes advocating for greater proof of citizenship before voting. But those standards would require access to documents like birth certificates or passports that may not be accessible to everyone.

Speakers at the march also denounced a Supreme Court decision in April to strike down key provisions of the Voting Rights Act of 1965, a landmark piece of civil rights legislation.

The law was designed to crack down on practices that disenfranchised Black voters. For decades, it had prevented lawmakers from redrawing congressional districts based on race.

But in April’s ruling, the court’s conservative majority argued it was impossible to “disentangle race from politics”. It therefore declared that a congressional map could be struck down only when there was evidence that states had “intentionally” limited opportunities for non-white voters through “strong interference”.

Critics say that new legal standard effectively made discrimination on the basis of race legal for the purposes of drawing voting maps.

In the aftermath of the court’s ruling, a number of Republican-led states passed new congressional maps to favour their party, often by carving up majority-Black districts.

In a letter, Reverend Al Sharpton, an organiser of Friday’s march, drew a line between the fight for voting rights during the civil rights era and the present-day circumstances.

“We stand on the same ground because the work is not finished,” Sharpton said, referring to the site of the 1963 march. “The right to vote, the very foundation of our power, is being chipped away in statehouse after statehouse. When the vote is weakened, every other right grows fragile with it.”

Senator Bernie Sanders, a progressive leader, also told the crowd that the “dream of a more just and equitable society has never been under greater threat than it is right now”. He denounced Trump for his actions to weaken voting rights.

“Today, we have a president along with the Supreme Court members he appointed carrying out the most significant assault on voting rights since segregation, targeting virtually every aspect of the electoral system,” Sanders said.