Overview:

Roughly one in 10 voters will cast ballots in newly configured congressional districts. For Black communities, the changes could determine whether their political strength is concentrated, divided or diminished.

When millions of Americans vote in November’s midterm elections, they may find that the district they knew — and the political power they once held — has disappeared.

Congressional maps have changed in nine states since the last federal election, shifting roughly one in 10 voters into newly configured districts, according to The Associated Press. New boundaries will be used in Alabama, California, Florida, Louisiana, North Carolina, Ohio, Tennessee, Texas and Utah.

LEARN MORE: The Fight for the Black Vote Is Already Underway

Redistricting typically is done once a decade, after the census determines where people have moved and how many congressional seats each state receives. This time, however, many changes occurred mid-decade — without a new census, in red states — at the urging of President Donald Trump, who sought an advantage in the battle for control of Congress. Democrats retaliated, prompting a redistricting arms race. 

‘Packing’ and ‘Cracking’

Most of the new maps favor Republicans. And in several Southern states, the changes came after the U.S. Supreme Court weakened a central protection of the Voting Rights Act that allowed maps to be challenged if they dilute the political influence of Black voters.

For Black America, this is not simply another fight between Democrats and Republicans. A congressional district determines which communities vote together, which candidates can realistically win, and whether Black voters have enough collective strength to elect someone responsive to their concerns.

What Black voters could lose is not only a seat in Congress. They could lose leverage.

Mapmakers have two reliable ways to diminish Black voters’ influence.

One is “packing”— concentrating as many Black voters as possible into a small number of districts. Those districts may reliably elect Black representatives, but surrounding districts become whiter and less competitive.

A congressional district determines which communities vote together, which candidates can realistically win, and whether Black voters have enough collective strength to elect someone responsive to their concerns.

The other is “cracking”— dividing a Black community among several districts so its voters are a minority in each one. A neighborhood may remain physically intact, yet become politically fragmented and represented by lawmakers whose electoral survival does not depend on listening to those voters.

Locking Out Black Voters

That danger is particularly clear in Alabama. The state’s revised map eliminated one of its two majority-Black congressional districts and reduced the Black voting strength in the district represented by Democratic Rep. Shomari Figures. Rep. Terri Sewell’s district retained a narrow Black majority.

Louisiana offers another warning. The state is nearly one-third Black, but its latest redistricting fight created the possibility that Black voters could end up without a district where they have a realistic opportunity to elect their preferred candidate. Similar battles have unfolded in Florida, North Carolina, Tennessee and Texas.

The changes can affect more than Congress’s racial makeup. Representatives help determine federal spending and policy on Medicaid, public schools, environmental enforcement, voting rights, housing and criminal justice — issues that routinely have a disproportionate effect on Black communities.

A district designed to weaken Black voting power can therefore shape whose hospital remains open, whose neighborhood receives disaster aid, whether a polluted community gets federal attention and which schools receive resources.

Even voters who understand the stakes may not know that their district has changed. They may have a new representative, unfamiliar candidates, or a different polling location. Campaign organizations may have to rebuild voter lists and community relationships. Churches, fraternities, sororities, and civic groups that have spent years organizing in one congressional district may suddenly find their members scattered across several.

That confusion can suppress participation without anyone being formally denied a ballot. A voter who arrives at the wrong precinct, cannot identify the candidates or believes a familiar representative is still on the ballot may decide the process is not worth the trouble.

Don’t Wait. Have a Plan

For Black voters — who have long faced barriers, including strict identification requirements, polling-place closures, voter-roll purges and limits on mail voting — a last-minute map change adds another hurdle.

Black voters should not wait until Election Day to discover whether their district changed. They should check their registration, review an official sample ballot and confirm their polling place through their state or local election office.

Voters also should ask candidates direct questions: Which Black neighborhoods are now in the district? What relationships have they built there? How will they protect voting access? What is their record on health care, schools, environmental justice and economic opportunity?

RELATED: SCOTUS Voting Rights Decision is ‘About as Bad as It Gets’

The courts may describe redistricting as a dispute over lines, procedure and constitutional authority. But those lines determine power.

And when those lines divide Black communities or reduce their ability to elect candidates of their choice, what disappears from the map is more than a familiar district. It measures the political voice Black Americans fought generations to obtain — and now may have to fight to keep.

A veteran journalist, political analyst, and essayist, Joseph Williams has been published in a wide range of publications, including The New York Times, The Washington Post, Politico, The Boston Globe, The Atlantic, and US News & World Report. A California native, Williams is a graduate of the University Of Richmond and a former Nieman Fellow at Harvard University. He lives and works in metro Washington, D.C.