Why do political parties most often try to gerrymander voting districts? to gain a political advantage
to ensure an equal chance for all candidates
to prove they deserve the voters’ support to keep each voting district the same shape

a, or to gain a political advantage

Explanation:

it makes the most sence

"germany's geographic location was an advantage when it was on the offensive in the war because it was situated next to an extremely wide river, the rhine, which was difficult for the allies to cross."

a king decides to declare war on a neighboring country without the input of any advisers