in the running
Entered as a competitor in a contest. For example, Is Mary in the running for this election? The antonym, out of the running, means "not entered as a competitor," as in Ian is out of the running for the job now that he's living in another state. [Mid-1800s]
Having a chance to win, as in Mary's still in the running for the promotion. Again, out of the running means the opposite, as in He's too oldhe's out of the running. [Mid-1800s] Both usages allude to the entry and chances of a horse in a race.