New Jersey must scrap its unique primary ballot design, widely criticized as boosting the prospects of party-backed candidates, a federal judge ruled Friday, saying the “integrity of the democratic practice” was at stake.

The ruling shakes a foundational component of New Jersey’s primary election ballots, which tend to group candidates with party support in a single column. That means the names of those running without establishment backing could be left in places on the ballot that are difficult to find.

Opponents of the system argued it put a “thumb on the scale” for party-preferred candidates. The defendants in the suit — most of the state's county clerks who design ballots — argued primarily that they didn't have enough time to redesign them.

U.S. District Judge Zahid Quraishi granted a preliminary injunction sought by Democratic Rep. Andy Kim and two other candidates in a ruling that applies to the June 4 primary. It's unclear exactly what it means beyond that.

“The Court wishes to make clear that it recognizes the magnitude of its decision," Quraishi wrote. "The integrity of the democratic process for a primary election is at stake and the remedy Plaintiffs are seeking is extraordinary.

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Kim hailed the ruling in an emailed statement.

"It’s a victory built from the incredible grassroots work of activists across our state who saw an undemocratic system marginalizing the voices of voters," he said.

Mary Melfi, the Hunterdon County clerk, worried whether she'd have enough time to comply with the ruling, which she said she was still reviewing. She compared it to a homeowner being ordered to repaint their house on deadline.

“I’m going to order you paint it and you better get it painted in two weeks,” she said. “Can you get a painter? Can you get it done? What color is it? It's ridiculous."

Kim's suit came amid a contentious primary contest for the U.S. Senate seat being vacated by federally indicted U.S. Sen. Bob Menendez. New Jersey's first lady, Tammy Murphy, dropped out of the race Sunday, but up until then she enjoyed party leader backing in populous counties, meaning she would have had favorable ballot positions.

Kim, 41, is a three-term congressman from southern New Jersey's 3rd District who now finds himself in a strong position to be the state's next senator. Menendez has announced he won't run as a Democrat, though he left open the possibility of running as an independent bid if he's exonerated at trial.

Menendez, his spouse and three business associates have been charged with engaging in a bribery scheme in which prosecutors say the senator and Nadine Menendez took gold bars, cash and a luxury vehicle in exchange for helping associates get a lucrative business deal with Egypt. The Menendezes and two of the three business associates have pleaded not guilty. A third pleaded guilty and agreed to be witness in the case.

Advocates pushing for the end of preferential ballot positioning for party favorites — called county-line ballot design — cheered the judge's decision.

“It’s a new day in the history of New Jersey politics,” said Antoinette Miles, director of the state's Working Families Party.

Friday's ruling is the latest domino to fall against the only such ballot design in the country. Earlier this month, state Attorney General Matt Platkin said county line designs were unconstitutional and he wouldn't defend them. Legislative leaders, under intense pressure from the Democratic party base, agreed to consider legislation overhauling the law.

A timetable on when that might happen is unclear.