strong candidate; front runner; major contender
Used for a person or team considered very likely to win an election, competition, or selection process.
He is a strong candidate in the presidential election.
His name is being mentioned as a front runner for the next company president.
有力候補 refers to a strong contender who might win, while 本命 specifically means the top favorite most likely to win.
Compound of 有力 (influential, strong) and 候補 (candidate).