NARRATION: Its one of the darkest arts of electoral politics. And its perfectly legal.

CARTER WRENN: This is like original sin. Both sides are infected with it.

NARRATION: Gerrymandering. It has a surprising history and contentious future, as Republicans and Democrats battle over data from the 2020 census to redraw political maps to their candidates advantage.

ARCHIVAL (MSNBC, THE LAST WORD WITH LAWRENCE ODONNELL SHOW, 8-12-21):MICHAEL WALDMAN: The census data is the beginning of redistricting which is the beginning of gerrymandering season.

DALLAS WOODHOUSE: What it has become to mean is districts that I dont like, because somebody else drew them.

NARRATION: The former steel town of Tarentum in western Pennsylvania is a mix of working-class Republicans and Democrats. Former congressman Jason Altmire says thats given him a close-up view of how gerrymandering works.

JASON ALTMIRE (FORMER U.S. REPRESENTATIVE, D-PA): When I was in office, if you lived in this house you were my constituent. But if you lived on this side, your congressman was 60 miles away in Johnstown, Pennsylvania. Its a small town; theyre in the same school district. Theyre one community, except for the fact they were represented by two different members of Congress.

NARRATION: In the decade after each new census, states redraw their congressional and legislative districts. The party in power, whether Republican or Democrat, typically draws maps to protect its own members.

FORMER CONSTITUENTS OF JASON ALTMIRE:WOMAN: Well, if youre right there on that line, on that border, and if its a crazy district, it can become very confusing.MAN: But gerrymandering isnt a partisan problem. We see this in other states like Maryland where its been the Democrats in power and the Democrats drawing the map to essentially marginalize Republican power.

JEFFREY TOOBIN (CHIEF LEGAL ANALYST, CNN): Gerrymandering doesnt just determine how many Democrats and Republicans will serve. It determines what kind of Democrats and Republicans. It contributes to polarization. It makes the more liberal Democrats more likely to win. It makes the more conservative Republicans more likely to win. And they are less likely to cooperate with each other, and that gets us to the politics we have now.

JASON ALTMIRE: If youre a member of Congress representing that type of district, you dont hear different points of view. You hold a town hall meeting and all you ever hear is, Right on, keep doing what youre doing. And dont you dare compromise.

NARRATION: Gerrymandering has been around since the 1800s, but perhaps nowhere has it been more fraught than in North Carolina. One battle began more than 30 years ago, when the Supreme Court ruled that the legislature had drawn voting districts in a way that disadvantaged Black voters.

ARCHIVAL (ABC, WORLD NEWS TONIGHT, 6-30-86):PETER JENNINGS: And in one unanimous decision today the court said that North Carolinas redistricting plan violated the 1982 Voting Rights Act by reducing Black voting power.

NARRATION: The court ruled that under the Voting Rights Act, minority groups should have the opportunity to elect their preferred candidates to Congress.

ARCHIVAL (CBS, EVENING NEWS, 10-1-92):MEL WATT: I Need your help!

NARRATION: The remedy? New majority-minority districts, where minority residents of voting age made up more than 50% of the population.

ARCHIVAL (ABC, WORLD NEWS TONIGHT, 9-16-92):REPORTER: In several states, new snake-like district lines were drawn, linking together small pockets of Black voters.

ARCHIVAL (CBS, EVENING NEWS, 10-1-92):MAN: I feel like things are changing in the right direction.

ARCHIVAL:EVA CLAYTON: Just wanna say hello to you. Im running for Congress.

NARRATION: In the 1992 elections, the new majority-minority districts achieved their goal, and 17 new Black representatives were elected to Congress.

ARCHIVAL:REPORTER: The new Congress looks more like America than any other Congress in history.

ARCHIVAL (C-SPAN,1992):EVA CLAYTON: Hello America!

NARRATION: One of them was a North Carolina lawyer and activist named Eva Clayton.

EVA CLAYTON (FORMER U.S. REPRESENTATIVE): From 1901 to 1992, no Afro-American had ever represented North Carolina.So that was a beautiful historical moment.

ARCHIVAL (C-SPAN, 1992):EVA CLAYTON: We too sing America.

EVA CLAYTON: I felt privileged, I felt honored, and I felt humbled and blessed.

NARRATION: But for the Democrats, who controlled the redistricting process in North Carolina, there was a price to pay. By packing Black voters into a limited number of districts, there were fewer Democrats everywhere else. Republicans saw an opportunity to divide and conquer.

ARCHIVAL (CONSERVATIVE POLITICAL ACTION COMMITTEE, C-SPAN II, 1992):BEN GINSBERG (CHIEF COUNSEL, REPUBLICAN NATIONAL COMMITTEE): Let me tell you that The Voting Rights Act has the potential to really shake things up and frankly it is frightening to the Democrats.

CARTER WRENN (REPUBLICAN POLITICAL STRATEGIST): Very quickly, the Republican politicos figured out that if you drew three minority-majority districts, it meant there were three incredibly Democrat districts, which meant there were more Republicans in the other eight or ten districts.

JEFFREY TOOBIN: So the Republicans went to the African-American community, largely Democratic, and said, Lets make a deal.

ARCHIVAL (CONSERVATIVE POLITICAL ACTION COMMITTEE, C-SPAN II, 1992):BEN GINSBERG (CHIEF COUNSEL, REPUBLICAN NATIONAL COMMITTEE): In South Carolina, Blacks and Republicans are already talking about a crescent-shaped district through the southern part of the state.

JEFFREY TOOBIN: The alliance when it comes to redistricting between the Republicans, mostly in the south, and the African-Americans mostly in the south has been called the unholy alliance. The first sign of what a big deal the unholy alliance was was the 1994 elections.

ARCHIVAL (1994):NEWT GINGRICH (FORMER HOUSE SPEAKER, R-GA): We will keep our commitment to keep our half of the contract with the help of the American people.

ARCHIVAL (CNN, 1-1-95):RICK SANTORUM (SENATOR, R-PA): Theres a new wind blowing, and it is a majority for Republicans.

JEFFREY TOOBIN: You saw the white Democrats in the South losing seat after seat.

ARCHIVAL (CNN, 1-1-95):BERNARD SHAW: Voters sweep Democrats from power in midterm elections and give Republicans control of the House and Senate for the first time in 40 years.

CARTER WRENN: So its an irony. More African-American districts meant less Democrats were elected.

ANGELA BRYANT (FORMER NORTH CAROLINA STATE SENATOR): So its sort of like taking our fight against racism, and the advancements weve made and the laws weve used and literally turning them around on their head and saying, These are the laws you want and you fought for? Fine. Were going to implement them a hundred and fifty percent and see if you like that.

ANGELA BRYANT (DRIVING IN HER CAR): Let me hold the map.

NARRATION: Angela Bryant served in the North Carolina legislature from a carefully drawn district.

ANGELA BRYANT (DRIVING IN HER CAR): So on the left side is in my district. Its one of the few trailer parks thats still in the city.

NARRATION: After the Supreme Court ruled in Shaw versus Reno in 1993 that race couldnt be the predominant factor determining district lines, drawing districts that would allow a majority of minority voters became even more complicated.

ANGELA BRYANT: It always bothered me, in terms of gerrymandering, that there was what I call a finger that scooped down into what was otherwise my district, that interrupted the compactness, and scooped out the wealthier households, which are more white and Republican. In a micro sense both me and my community benefited from the racial gerrymander, in that I got to represent them. However, in the big sense, it rendered us powerless in that the surrounding white communities and representatives didnt need us, and they could label our party as the Black party.

NARRATION: In 2017, the courts ruled that Republicans in North Carolina had packed too many African American voters into too few districts, forcing them to redraw their maps again.

ARCHIVAL (CNN, 1-10-18):DON LEMON: North Carolina is really ground zero for gerrymandering

NARRATION: It was a victory for Democrats, but Angela Bryant decided not to run for re-election.

ANGELA BRYANT: People say, oh they pushed her out. They didnt push me out. Its a shift we helped design and we pushed for. The Republicans, they said, You realize if you fight this you lose your district, you know. And so Im saying, somehow youre missing the point. I say, its not my district thats important to me. Im against racism. Were insulted to have a district based on racial discriminatory practices.

NARRATION: With Republicans firmly in charge of mapmaking in many states, Democratic groups have gone to court over the years to challenge gerrymandering that they feel reduces their voting power.

DALLAS WOODHOUSE (FORMER EXECUTIVE DIRECTOR, NORTH CAROLINA REPUBLICAN PARTY): Democrats dont like the fact that Republicans took over a lot of State Legislatures, and what weve seen with Democrats across the country is to look for bogeymen under every rock they can to explain their electoral failures. And of course it is my opinion that Democrats want to use the courts to do what they cant win at the ballot box, and that is elections.

NARRATION: In 2019, the Supreme Court ruled that federal courts shouldnt have a role in determining partisan gerrymandering cases, leaving those decisions to state courts.

ARCHIVAL (MSNBC, VELSHI, 8-12-21):ALI VELSHI: The long-awaited results of the 2020 census, which will reshape the balance of power in the United States for the next decade, have just been released.

NARRATION: Despite calls from both sides to avoid partisan gerrymandering, legislators in states like Texas want to use the census data to create more Republican seats in Congress, while Democrats hope to do the same in states like New York, as control of the House of Representatives after the 2022 midterm elections hangs in the balance.

DALLAS WOODHOUSE: Heres what the Democrats need to do to fix their problem. They need to go when people back over in areas they lost, or they need to get the ones they have to move to other places.

JASON ALTMIRE: The problem that Democrats have is they have sorted themselves into like-minded communities, and it makes it very easy to draw lines that advantage the Republican Party because you can put all the Democrats into one single area, and thats not something thats going to change. Thats a social trend that is greater and more impactful than just gerrymandering.

EVA CLAYTON: In a democracy, what we have as a final tool are our votes. Thats how people express themselves.

NARRATION: Fifty years ago, before the days of majority-minority districts, Eva Clayton ran for Congress and lost.

ARCHIVAL (12-13-68):EVA CLAYTON: When you find people who are in tears because you lost, then you know that you have not only stirred the emotions but also the hope.

NARRATION: Today, the former Congresswoman feels that a minority candidate could run and appeal to everyone, even as she says gerrymandering by both parties has skewed the electoral process.

EVA CLAYTON: There ought to be some line that you dont cross. How far would you go to control? Taking advantage of the election is expected, but the prize of winning also has within it core responsibility fairness and respect for the rule of law.