WASHINGTON — Democrats filed lawsuits against the Donald J. Trump campaign and other Republicans to stop potential voter intimidation at the polls in four battleground states.

The complaints — filed Sunday by state Democratic parties in Nevada, Pennsylvania, Ohio and Arizona — came nine days before the presidential election and allege a “coordinated campaign of vigilante voter intimidation” that violates the Voting Rights Act of 1965 and the Ku Klux Klan Act of 1871, which bans private conspiracies to intimidate or threaten voters.

They ask the court to stop activities at election sites by the state Republican parties, the Trump campaign, longtime Trump adviser Roger J. Stone and a group called Stop the Steal Inc. formed by Stone.

“Trump’s calls for unlawful intimidation have grown louder and louder, and the conspiracy to harass and threaten voters on Election Day has already resulted in acts that threaten the voting rights of registered Pennsylvania voters,” the Pennsylvania complaint states.

The lawsuits cite an unnamed official’s comments to Bloomberg News last Thursday that the Trump campaign has three voter suppression operations that target African-Americans and other groups. And the Democrats allege Trump supporters have pledged to go to certain polling places with minority voters and interfere.