In states there have been districts that are spread out like a snake through poor and urban areas so that minorities are confined to a single or a few districts. The Republicans realize that voters in these areas most often vote for Democrats. The Republicans have to influence the redistricting committee to create these ‘gerrymandered’ districts so that the Republicans can confine the Democratic voters to fewest districts and allow Republicans to dominate the legislatures. In other words, by causing the districts to be accommodating to their reelection, the Republicans gain seats in the legislature and they don’t fairly represent their constituents.
I’m not saying that Republicans are the only ones that do this. But the court case against Gerrymandering in central Florida is against a redistricting committee that is controlled by Republicans.
The Republicans try their best to put blocks to voting rights for minorities. They think that a most of minority voters vote for democrats, so the want to limit as much as possible the ability of minority voters to vote.