Gerrymandering is the practice of redrawing political boundaries in order to gain electoral advantage. The usual strategy is to draw the lines such that voters likely to oppose one's own party are all grouped together in as few districts as possible, while the voters who are likely to support that party are spread across as many districts as possible – so as to carry as many districts as possible in that party's favor – while still remaining a majority in each such district.
A more serious problem arises when the politicians who are elected within a system have the authority to affect the political boundaries which will be used in the next election, or even in the election of others with whom they might gainfully trade "favors", in effect giving long-term job security to incumbents of both parties and thus maintaining the two-party system.
Imagine if Pepsi and Coke had arranged to divide up the cola market into tidy little local geographic monopolies, where each could charge whatever they liked for colored sugar water... while claiming that their nearly 50:50 overall split means "healthy competition"! Hell, they could even do this while hating each other's guts, the same way that democrats and republicans now do.
- Georgia's 12th District: an almost-reasonable oblong running down the GA/SC border from Augusta to Savannah... but with a little tentacle reaching out to Athens
- Conservapedia claims that gerrymandering helped Thomas Jefferson win the presidency -- true, or just a reflexive dig at a liberal icon? The term originated later on, but was the practice commonplace before Elbridge Gerry made it famous?