In horse racing, an entry heavily favored to win a dubious or manipulated race is often called a shoo-in. A political candidate with no significant competition or a senior employee clearly qualified for a promotion could also be called a shoo-in for the new position. A shoo-in often holds such a commanding lead over the nearest competitor or such an impressive reputation in the field that the results are almost inevitable.
This seemingly guaranteed result of a lopsided contest is one reason some overqualified entrants refuse to enter the competition. When a competitor in a sporting event or a candidate in a political election becomes viewed as a shoo-in, he or she may no longer feel a need to put forth a maximum amount of effort. A shoo-in often dominates the field to the point where the real competition is for second place or another form of consolation prize.
Some sources incorrectly spell the term as shoe-in, suggesting a different horse racing or foot racing origin. In fact, the correctly spelled shoo-in comes from the verb to shoo, meaning to steer or manipulate something in a specific direction. A skilled jockey could shoo his horse around other competitors on the track and win the race handily. Running a more experienced or powerful horse against an inexperienced field almost always guaranteed a "shoo-in," and those in the know would place bets accordingly.
To be considered a shoo-in for a job promotion or a elected position is generally a positive thing, but it can also create additional pressure for the favored candidate. A person considered a shoo-in cannot assume a win is absolutely guaranteed, even when facing minimal competition. A shoo-in candidate benefits from strong public support and a demonstrated record of success, but also has an obligation to remain above reproach until the final results are in.
In general, a shoo-in benefits from both internal and external factors to enjoy his or her victory over the competition. Quite often a potential candidate is convinced to enter a race because of his or her perceived status as a shoo-in, whether or not the claim turns out to be accurate. Many people like a sure bet or a guaranteed success, and that's precisely what a shoo-in candidate aspires to deliver.