Lets start by defining the term correctly:
Gerrymandering, in U.S. politics, the practice of drawing the boundaries of electoral districts in a way that gives one political party an unfair advantage over its rivals (political or partisan gerrymandering) or that dilutes the voting power of members of ethnic or linguistic minority groups (racial gerrymandering). The term is derived from the name of Gov. Elbridge Gerry of Massachusetts, whose administration enacted a law in 1812 defining new state senatorial districts.
The effects are pretty clear in our country. Here you will be able to see the effects of resizing and redrawing that could change and swing the voting criteria. Now this website is heavy on statistical analysis and has some pretty fancy algorithms but if you spend enough time with it you may be able to understand the effects it has on the political spectrum and we can make some assumptions based on the redrawing the “swing” that would occur.