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Running Mate from WikiPedia:

A running mate is a person running together with another person on a joint ticket during an election. The term is most often used in reference to the person in the subordinate position (such as the Vice President running with a presidential candidate) but can also properly be used when referring to both candidates, such as "Michael Dukakis and Lloyd Bentsen were running mates in 1988".

The term is usually used in the United States, in reference to a prospective Vice President. In some states, candidates for lieutenant governor run on a ticket with gubernatorial candidates, and are also known as running mates.

In the United States, a running mate is usually a reference to a candidate for the vice presidency, whom the candidate for president nominates, sometime in late August, and who is then formally endorsed (usually unopposed) by the party's convention. The term is also applied in U.S. states where the governor and lieutenant governor run together on the same ticket.

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