It's not a perfect analogy, but since it's been used by the Clinton camp frequently, it's fair game.
Rocky Balboa is introduced as a small-time boxer and collector for a loan shark. The World Heavyweight Championship bout is scheduled for New Year's Day, 1976, the year of the United States Bicentennial. When the opponent of undefeated heavyweight champion Apollo Creed is injured, Creed comes up with the idea of fighting a local Philadelphia underdog and, because he likes Rocky's nickname, "The Italian Stallion," he selects the unknown fighter.
To prepare for the fight, Rocky trains with 1920s-era ex-bantamweight fighter Mickey Goldmill, while Rocky's best friend, Paulie, a meat-packing plant worker, lets him practice his punches on the carcasses hanging in the freezers. During training, Rocky dates Paulie's quiet sister, Adrian. The night before the fight, Rocky confides in Adrian that he does not expect to beat Creed, and that all he wants is to go the distance with Creed, meaning last 15 rounds against him (the typical scheduled length of championship fights at the time).
Creed does not initially take the fight seriously, but Rocky unexpectedly knocks him down in the first round and the match turns intense. The fight indeed lasts 15 rounds with each fighter suffering many injuries.
It's now the morning after the big fight. Everyone had counted Rocky (played by Hillary) out, but after 15 rounds in the ring with Apollo (played by Barack), Rocky proved that you never give up, even in the face of insurmountable odds and pressure, that you have to keep fighting until the final bell is rung. Only then can you tell who won in this pugilistic contest of strength, endurance and will power.
If you've seen Rocky, I don't need to remind you of the full story. Or how it ends.
After 15 rounds...Rocky loses to Apollo.
Yes, it's on points, as no one got the knockout punch, but Apollo won.
Hillary won the round, but when all the points are added up in the end, Obama will have won the fight.