A conservative legal watchdog group said it will sue the state of Maryland unless it takes more aggressive action to remove ineligible voters from the registration rolls of Montgomery County, its largest jurisdiction.

In a letter to the Maryland State Board of Elections last week, Judicial Watch cited data showing that there are more registered voters in Montgomery than there are citizens of voting age (18 and over). The group called it “strong circumstantial evidence” that the state’s rolls are swollen by voters who are deceased, have moved away or who are not citizens.

Judicial Watch has made similar allegations in more than 90 counties in 11 states, including North Carolina, Florida and Kentucky. Montgomery County, where Democrats have a 2-to-1 registration advantage — is the only Maryland county that was served notice. The group said it will file a lawsuit against Maryland within 90 days unless the state takes corrective action.

“Your failure to maintain accurate, up-to-date voter registration lists has created the risk that the 2018 federal elections will lack the integrity required by federal law and by the expectations of Maryland citizens,” Judicial Watch President Thomas Fitton said in the April 11 letter to board chairman David McManus Jr.

Maryland officials said they are reviewing the letter, but elections administrator Linda Lamone said in a statement Tuesday that she is confident that the state and local elections boards are complying with the National Voter Registration Act, also known as the motor voter law, which is designed to expand access to voting.

“Federal and state law lays out a process for list maintenance of the voter registration database that the local boards of elections in Maryland are instructed to follow,” Lamone said. “We here at the state board regularly audit the local boards’ compliance with the process as part of our oversight role.”

The board is scheduled to discuss the Judicial Watch letter at its meeting on Thursday.

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The action by Judicial Watch is the latest in a fight that has raged for years in courts and statehouses over claims from the right that the country’s voting and registration systems are rife with fraud and neglect. Experts acknowledge that registration rolls are often out of date, but they say that charges of widespread voting fraud are baseless.

President Trump renewed the charges shortly after taking office in January, when he claimed in a tweet that between 3 and 5 million people voted illegally in November. He tasked Vice President Pence with heading an investigation into the matter.

[Analysis: Donald Trump’s indefensible claims of rampant voter fraud are now White House policy]

At the state and local levels, officials have cited concerns about fraud to enact stricter voter-ID laws and in some cases mass purging of voter rolls — measures that critics say are aimed at suppressing minority voting.

Wendy Weiser, director of the Democracy Program at the Brennan Center for Justice at New York University School of Law, said the Judicial Watch action is part of that larger effort to coerce states into aggressively purging voter rolls.

“This has often been used as a technique to try to suppress votes,” Weiser said. “It seems a little more like a stunt than a serious effort.”

Fitton said in an interview Tuesday that Weiser’s criticism is “just slander” from the left.

“They’re playing the race card to steal elections,” he said. “This is a straightforward federal law, and the law requires that [voter rolls] be cleaned up.”

Judicial Watch has succeeded in compelling some states to overhaul their rolls. In 2012, Ohio Secretary of State Jon Husted entered a settlement with Judicial Watch and True the Vote, a conservative vote-monitoring organization, to make certain changes in its management of voter lists.

Among them was an agreement to use the Interstate Voter Registration Crosscheck, a program created by Kansas Secretary of State Kris Kobach back in 2007. About 30 states, most of which have Republican secretaries of state, use the system to compare voter rolls for duplicate entries. Kobach has been among the most aggressive state officials in pursuing cases of alleged voter fraud, obtaining eight convictions since gaining the authority to prosecute such cases in 2015.

Records show that Montgomery’s total registration of 657,548 is higher than its voting-age population of 633,295. But county and state officials said the numbers reflect the lengthy process that states are required by law to employ when verifying voting status.

A voter is placed on inactive status after two sample ballots are mailed and returned to the state with no forwarding address. Voters are removed from the rolls after not voting in two consecutive federal elections.

The state also collects death notices, felony convictions and information about residents who have moved out of state, and it passes those on to county election boards, which are responsible for making the actual changes every month.

Montgomery’s March report shows 15,294 voters placed on inactive status and 758 removed from the rolls.

“I can tell you that Montgomery County follows every rule and regulation making sure that every ineligible voter is removed from the rolls,” said county election board president James Shalleck.

Fitton said most counties don’t have numbers like Montgomery’s.

“Following federal law shouldn’t result in the numbers Montgomery County has,” Fitton said. Judicial Watch has asked for records and further explanation from the state.

“If we can get the list cleaned up without litigation that would be great,” he said.