Ohio Democrats filed a federal lawsuit to prevent GOP presidential candidate Donald Trump and Ohio Republicans from intimidating voters – something state and federal law already does.

The complaint alleges Trump – with help from Florida GOP political operative Roger Stone and the Ohio Republican Party – has called on supporters to act as vigilantes and intimidate Ohioans trying to vote. Ohio Democrats fear Trump's supporters will target African-American voters in Democratic-friendly areas such as Cleveland and Columbus in violation of the Ku Klux Klan and Voting Rights acts.

But state and federal laws already prohibit voter intimidation, and Ohio Democratic Party Chairman David Pepper said he hasn't heard of any problems this year.

"We are very confident that people will be able to vote free of intimidation and harassment," Pepper said.

So why file a lawsuit? "We don’t want to take anything for granted," he said.

Trump's website has recruited election observers with the slogan: “Stop Crooked Hillary From Rigging This Election!” The political action committee run by Stone, a longtime Trump ally, created StoptheSteal.org to find poll watchers. The website promises to inspect polling software and engage in exit polling. "If this election is close, THEY WILL STEAL IT," it says.

But Ohio Republicans called the lawsuit "nothing more than a publicity stunt."

"The arguments cited are not at all related to our official operations at the Ohio Republican Party," spokeswoman Brittany Warner said. "Republican leadership in Ohio has created opportunities for greater ballot access and in no way would we ever be involved in the intimidation of voters."

The lawsuit is one of several filed by Democrats in swing states, such as Nevada, Pennsylvania and Ohio. Ohio remains a tight race between Trump and Democrat Hillary Clinton, according to recent polls. Ohio's 18 electoral college votes are must-win for Trump, because no Republican has won the White House without winning Ohio.

The lawsuits accuse Trump of encouraging "vigilante voter intimidation."

"Trump’s calls for unlawful intimidation have grown louder and louder, and the conspiracy to harass and threaten voters has already resulted in acts that threaten to interfere with the voting rights of registered Ohio voters," according to the filing.

Democrats say they aren't concerned about election observers, who are individuals selected by parties and campaigns to watch the election process. Those observers have strict rules, such as no phone calls and no weapons. They must be certified and take an oath. Democrats are worried about unauthorized people taking the call to prevent election rigging into their own hands.

Democrats asked a federal judge to declare threats, "aggressive questioning" of those waiting to vote and other forms of intimidation are not permitted under state and federal laws. They also want Trump's campaign, Stone's group and Ohio Republicans banned from organizing groups that could potentially threaten voters. Any decision from the judge should be publicized to police and election officials, the Democrats say in their filing.