In 1812, governor Elbridge Gerry from Massachusetts modified voting districts to help his party win elections. By the eyes of a Boston Gazzete cartoonist, one of the districts resembled a salamander. (Note: it was a mystical salamander, not the common fire salamander, see photo.) The local newspaper printed the cartoon and called the district Gerry-mander. Besides, it also criticized the changes. So, the phrase gerrymandering was born.
Thus, it is an unfair election practice. The idea behind it is simple. Elections take place in districts. In each of these “precincts,” there is a set amount of mandates (seats). Of course, every political party wants to win in as many of these districts as feasible.
To elevate their chances for success, the party or politician currently in office analyzes people’s views. When the party gathers enough data, they modify the districts. According to the data, they should have much higher chances of success.
Most of the time, gerrymandering is easy to spot. The new districts have uncanny shapes and disrespect common and natural borders. Besides, they tend to have a very different amount of voters. So, each vote has a distinct value. That threatens the integrity of elections in a crucial way.
Lastly, the practice is most common in a plurality voting system.
Gerrymandering in practice
Possibly, the practice is most common in the USA, the UK, and Northern Ireland. Besides the 1812 incident, it transpired many more times in America. For example, it was sometimes used as a segregation tool to undermine Black communities. In 1970s Northern Ireland, the practice tried to discriminate against Catholics for the benefit of Protestants.
If the whole country is one district, gerrymandering is easy to prevent. That is the case for Israel. Besides, the proportional voting system thins the margins for the practice.