Saying they are being disenfranchised, two voters — one independent, another Republican — filed a federal lawsuit on Friday asking a judge to open the Aug. 14 Miami-Dade State Attorney’s election to voters of all parties.

Longtime incumbent Katherine Fernández Rundle is being challenged by fellow Democrat Rod Vereen, a race that would have been open to all voters because no Republicans or independents filed to run.

But two write-in candidates — who have not campaigned, did not have to pay filing fees and will not appear on the ballot — filed to run just before the April filing deadline. Under a controversial and much-criticized state election rule, their entry served to close the primary race to just 525,890 Democratic voters.

Friday’s lawsuit was filed against Penelope Townsley, Miami-Dade’s election supervisor. The plaintiffs: Vincent J. Mazzilli, an independent voter who is the former Drug Enforcement Administration’s Miami special agent in charge, and Republican Armando Lacasa, a former Miami commissioner.

More than 700,000 of the county’s 1.3 million voters will be shut out because of the “gimmick” used to close the primary, according to the suit filed by law firm Colson Hicks Eidson. The suit asks a federal judge to hold the election law unconstitutional.

“Never before has a blank space on a general election ballot operated to close a winner-take-all State Attorney primary in the State of Florida,” the lawsuit reads.

The write-in candidates are lawyers Michele Samaroo and T. Omar Malone, neither of whom have actively campaigned or returned phone calls from the press.

Fernández Rundle, the state attorney since 1993, has accused Vereen’s campaign of running the write-ins to cut off Republican and independent voters from whom she enjoys general support.

Vereen denied that and accuses her of being a “wolf in sheep’s clothing” by urging Republicans and independents to switch to the Democratic party to vote for her. He insists that he will face Samaroo and Malone in the November election if he wins the primary.

Vereen’s campaign, on Friday, declined to comment. Fernández Rundle said she was familiar with the lawsuit. “It’s a good thing for our community that nobody be disenfranchised. It’s been used as bad public practice and I think this is a civil rights issue.”

Political analysts have long criticized write-in candidates as political ploys.

In 1998, Florida voters overwhelmingly voted to change the state’s constitution, opening primary races to all voters if a candidate did not draw a challenger from the opposing party or independents in the general election. The idea was to make sure all voters could participate in choosing their elected officials.

But in 2000, the state’s elections division issued an advisory opinion that decided that one single write-in candidate could close a primary.

The federal lawsuit points out that number of campaigns featuring write-in candidates skyrocketed in the 10 years after the state issued its opinion, a 337-percent jump from the previous six years.

The lawsuit points out that no write-in candidate has ever come close to winning a Florida election. The most votes a Miami-Dade write-in has ever received in a general election: 462, in House race in 2010.

The lawsuit also includes a sworn affidavit from Rod Smith, the head of Florida’s Democratic Party, which says that the party is not taking a position on whether the race should be open or closed.

“I would like to vote for state attorney. I will be disenfranchised,” said lawyer Roberto Martinez, a prominent Republican and former U.S. attorney in Miami, who filed the suit. “When the plaintiffs found out, they were outraged. They also want to have a say in the election.”