running mate
[noun]
Synonyms: associate, buddy, chum, comate, companion, comrade, crony, cully, pal

[TahlilGaran] English Synonym Dictionary ▲

ˈrunning mate noun [countable usually singular]
the person chosen by someone who is trying to become president, leader etc to help win an election, and be the second most important political person if they are elected

[TahlilGaran] Dictionary of Contemporary English ▲