Check out the Brennan Center's work on what redistricting means in New York.
And, check out this NYTimes story:
How to Tilt an Election Through Redistricting
By MICHAEL COOPER
It was a gerrymander too ambitious for its own good.
When Pennsylvania lost two seats in Congress to the booming Sun Belt in 2000, the Republicans who controlled state government redrew the map of Congressional districts to pack Republican voters into as many districts as possible.
At first, the strategy worked. In the next election, the state’s delegation shifted to 12 Republicans and 7 Democrats, from 11 Republicans and 10 Democrats. Furious Democrats challenged the new map but the Supreme Court upheld it.
Instead of drawing, say, 11 Republican districts with comfortable margins of Republican voters, party strategists had tried to draw 12 or 13 Republican districts, but with slimmer margins. As it turned out, those margins were a bit too narrow, and, by 2006, Democrats had won those districts. The state now has 12 Democratic and just 7 Republican districts, the reverse of what the Republican gerrymander originally accomplished. “They took a risk, and it backfired,” said Edward G. Rendell, Pennsylvania’s Democratic governor.
Now, with the 2010 census complete, Democrats and Republicans across the country are preparing for another once-a-decade exercise in creative cartography. To gain the upper hand in the next redistricting, Pennsylvania Republicans are fighting to win back the governor’s mansion and the state’s House of Representatives. Independent analysts say a Republican surge in statehouses around the nation could leave them with the power to redraw as many as 25 Congressional seats in their favor.
So what are the tricks of the trade? Why do so many districts end up as misshapen Rorschach inkblots with nicknames like “the Earmuff,” “the Flying Giraffe,” or, in the case of a State Senate district in upstate New York, “Abraham Lincoln Riding on a Vacuum Cleaner”?
Both parties rely on sophisticated computer programs, savvy political operatives and election lawyers to push their maps through the frequent court challenges. But the basic principles of gerrymandering — known to the pros as “packing” and “cracking” — are simple, and used often.