Republican presidential front-runner Donald Trump waves to a cheering crowd during a campaign stop Tuesday in New Hampshire. (Jim Cole/AP)

Three African American pastors who support Donald Trump filed a federal lawsuit Wednesday over a requirement that GOP primary voters sign a statement affirming that they are Republicans — a plan the presidential front-runner has condemned.

The plaintiffs say the loyalty pledge will discourage minority voters and those who are poor from casting ballots in Virginia, where voters do not register by party. Signing the vow will create long lines at the polls, imposes “the burden of fear and backlash” and amounts to a literacy test, according to the lawsuit.

The Virginia Republican Party recently decided voters who want to help choose the Republican presidential nominee must first sign a statement that says: “My signature below indicates I am a Republican.”

Virginia Beach attorney Chester Smith said his clients — Stephen A. Parson Sr., Bruce L. Waller Sr. and Leon Benjamin — are Richmond-area pastors who decline to say if they have supported Democrats in the past. The complaint was filed in Newport News, but it will be heard in Richmond, he said.

“I imagine they ascribe to a lot of the message that Donald Trump brings and . . . the idea of making the country great again and making values important again,” Smith said.

Business mogul and presidential candidate Donald Trump announced he signed the loyalty pledge that the Republican National Committee has demanded of its candidates during a news conference at Trump Tower in Manhattan. (Reuters)

The lawsuit names the three members of Virginia’s Board of Elections as defendants because they finalized and will oversee the administration of the pledge at the polls. Martin Mash, a spokesman for the state’s Department of Elections, declined comment.

Trump brought the issue to national prominence last week when, in a series of tweets, he called the oath a “suicidal mistake” that would “disallow independent, unaffiliated and new voters. BAD!”

In a statement from Trump’s campaign, the celebrity billionaire said he had nothing to do with the lawsuit but that he supports the pastors’ cause.

“If they don’t stop excluding people, the party is doomed,” Trump said. Democratic presidential candidate “Hillary [Clinton] and the Democrats love this. The Republican Party in Virginia keeps losing. They really need to be smart and win for a change.”

The pledge could be particularly damaging to Trump, whose un­or­tho­dox candidacy has attracted voters disenchanted with traditional party politics, experts have said.

Trump’s criticism has exacerbated division within the state GOP, whose governing body voted for the pledge in September. Several activists who previously supported the pledge have since reversed their position and advised the party to withdraw it.

“It’s time to pull the plug on this disaster,” Russ Moulton, an influential conservative activist, said of the oath last week.

Despite recent attempts to impose a pledge in presidential primaries, the last one was instituted in 2000, according to party officials.

GOP officials declined to comment Wednesday on whether the public outcry and the lawsuit have caused them to reconsider.

Last week, John Findlay, executive director of the Virginia GOP, sent party officials talking points insisting that the pledge, which the party calls a “statement of affiliation,” is intended to prevent Democrats from choosing the party’s nominee.

“For reasons unknown to our Party at this time, Donald Trump has decided that this [is] an attack against his campaign,” he said in the email. “Let me be very clear, the statement of affiliation is not designed to favor or hurt any candidate whatsoever.”

The lawsuit, which was first reported by the Richmond Times-Dispatch, says the pledge violates the Voting Rights Act, the equal protection clause of the 14th Amendment, the First Amendment and state law.

The pledge will cause long lines, the suit says, and poor people, who the lawsuit says are disproportionately black and Hispanic in Virginia, cannot afford to wait for hours to vote. The lawsuit also says the problems are exacerbated by Virginia’s history of slavery, poll taxes and school segregation.