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.