In Virginia, members of a bipartisan panel were entrusted with drawing a new map of the state’s congressional districts. But politics got in the way. Reduced to shouting matches, accusations and tears, they gave up.

In Ohio, Republicans who control the legislature simply ignored the state’s redistricting commission, choosing to draw a highly gerrymandered map themselves. Democrats in New York are likely to take a similar path next year.

And in Arizona and Michigan, independent mapmakers have been besieged by shadowy pressure campaigns disguised as spontaneous, grass-roots political organizing.

Partisan gerrymandering is as old as the republic, but good-government experts thought they had hit on a solution with independent commissions, advisory groups and outside panels. Taking the map-drawing process out of the hands of lawmakers under pressure to win elections, the thinking went, would make American democracy more fair.

But as this year’s once-in-a-decade redistricting process descends into trench warfare, both Republicans and Democrats have been throwing grenades at the independent experts caught in the middle.

In state after state, the parties have largely abdicated their commitments to representative maps. Each side recognizes the enormous stakes: Redistricting alone could determine which party controls Congress for the next decade.

In some states, commissions with poorly designed structures have fallen victim to entrenched political divisions, leading the process to be punted to courts. In others, the panels’ authority has been subverted by state lawmakers, who have either forced the commissioners to draft new maps or chosen to make their own.

New York Democratic state legislators, who can override the state’s independent redistricting commission with a supermajority vote, have disregarded the draft proposal that the commission made public in September. In Wisconsin, where a court battle over redistricting is already unfolding between Republicans who control the Legislature and Gov. Tony Evers, a Democrat, the State Assembly speaker, Robin Vos, dismissed the governor’s People’s Maps Commission.

“There is no such thing as a nonpartisan commission,” Mr. Vos, a Republican, said at a hearing last month. All commissioners are partisan, he said. “If they vote, they vote for someone in one of the two parties.”

For decades, well-meaning people saw independent commissions as a crucial way to eliminate gamesmanship that exasperates many voters and distorts American politics: the incumbency protection, the devaluing of people’s votes, the polarization and stridency that it all fuels.

As a supposed fix, the independent panels were never entirely insulated from politics. The changes were often supported by Democrats, who felt overmatched by Republican majorities in statehouses and by G.O.P.-drawn maps that seemed to set those partisan tilts in stone.

But in the current environment, the fix has frequently fallen short.

Some independent commissions have found success: Colorado recently passed a map that redistricting experts saw as evenhanded, and early drafts out of Arizona were also given high marks for fairness. Even in states like Virginia where the process has been rocky, nonpartisan groups working to end gerrymandering say that the commissions have been an improvement.

“If politicians are given leeway to draw partisan maps, they’re going to do it,” said Ally Marcella, a research analyst at RepresentUS, a nonpartisan group focused on redistricting and electoral overhauls.

During the 2010s, Democratic groups in states where the party was locked into statehouse minorities tried, with some success, to create outside redistricting bodies to wrest some power from Republicans.

After Michigan voters created a commission through a ballot initiative in 2018, the state’s Republican Party sued to halt its formation. The party lost.

Last week, Utah Republicans adopted their own maps, ignoring proposals from a redistricting commission that voters approved in 2018. On Monday, Washington State’s redistricting commission missed a deadline to finish its maps, sending drawing authority to the State Supreme Court.

And in Iowa, where nonpartisan career staff members in the Legislature have been drawing maps since 1980, Republican state lawmakers rejected this year’s first proposal, which would have given Democrats an advantage in two of the state’s four congressional seats. Lawmakers later approved a second map proposed by the staff in which all four districts were carried by former President Donald J. Trump in 2020.

When Michigan’s commission began its work this year, a new group called Fair Maps emerged, with numerous former Republican officials on its payroll. The state G.O.P. and Fair Maps held training sessions where they instructed allies to lobby for preferred maps.

During a virtual training session in October, Meghan Reckling, an official with Fair Maps in Michigan who is also a Republican county chairwoman, instructed those attending to push for the “Maple map” (all Michigan commission map proposals are named after trees) because it was best for the party.

“We can do good candidate recruitment, raise money, share our message with the residents in those districts, and have hopefully a path to majority of the congressional delegation from there with the Maple map,” she said during the training, according to audio reviewed by The New York Times.

Democratic officials offered similar training. An email from the Washtenaw County Democratic Party urged supporters to flood an online comment section to support the “Cherry map.”

Officials in the Democratic and Republican state parties argued that they were simply helping ordinary citizens have a say in the process.

“All of our comments are leading toward, ‘Let’s make the maps fair,’ as opposed to, ‘This is how we draw a map that will make sure that we elect all Democrats,’” said Lavora Barnes, the chairwoman of the Michigan Democratic Party.

Gustavo Portela, a spokesman for the Michigan Republican Party, emphasized that Fair Maps was not part of the party.

In Arizona, where voters in 2000 approved a constitutional amendment creating an independent redistricting commission, the public comment process this year was flooded with nearly identical comments pushing partisan narratives on both sides, identified in a report by the Center for Public Integrity. And it began well before lines were even drawn.

Many of the comments could be traced to a Telegram account belonging to a conservative group called Arizona Red Roots, as well as a Facebook post by a local Republican women’s club, identified in a report by the Center for Public Integrity.

Erika Schupak Neuberg, an independent chairwoman of the Arizona commission, said the campaigns were easily recognizable — and also welcomed.

“If any organization is capable of rallying a passionate group, I want to know who they are,” she said. “I want to know the numbers because that’s a community of interest.”

Some redistricting commissions have tried shielding themselves from lobbying and influence campaigns. In Colorado, the secretary of state’s office accused three men with ties to the state’s Republican Party of trying to sway redistricting without properly registering as lobbyists.

“There was definitely a battle for influence of the 12 commissioners,” said Simon Tafoya, a Democratic commissioner.

But as in Arizona, commission members in Colorado said that it was easy to spot influence being peddled by either party, and noted that the presence of unaffiliated members on the commission with no ties to either party had helped offset any attempts by partisan members to coordinate an outside campaign.

“You can’t take the politics out of redistricting,” said Bill Leone, a Republican member on the Colorado commission. “There’s no way to make redistricting not a zero-sum game.”

Perhaps nowhere was that difficulty more apparent than in Virginia. The state’s 16-member commission was split between eight legislators and eight citizens, with equal representation of Democrats and Republicans and no independents.

Since its inception, the commission has deadlocked 8-to-8 on nearly every vote, on everything from procedural rules to the designs of potential maps. At one point, three Democratic members stormed out of a meeting to prevent a quorum.

“Virginia is a bipartisan commission, but with the partisans selected by the political leadership of the two houses in the General Assembly — so it’s not only partisan, but it’s hyperpartisan,” said Marcus Simon, a Democratic state legislator who sat on the commission. “So you’re getting the most trusted partisans the other party has to offer and sending them in to duel, as opposed to compromise.”

The commission spiraled further downward when Mr. Simon accused former Representative Tom Davis, a Republican, of receiving assistance on a proposed map from the National Republican Redistricting Trust, a group central to the party’s efforts to influence redistricting across the country. Republicans on the commission had accepted Mr. Davis’s map as one that they wanted to consider, leading Mr. Simon to accuse them of “collusion.”

Mr. Davis said in an interview that he had drawn the map himself but that the Republican group had helped him submit it because, he said, he is “a bit of a technophobe.”

The commission’s work ended in gridlock, and the process was punted to the Virginia Supreme Court. Last week, both parties in Virginia nominated candidates to help the court in drawing the maps.

Among the Republican nominees: Adam Kincaid, the executive director of the National Republican Redistricting Trust. The court rejected his nomination.