A horse race is a competition in which horses run against each other for a purse of money. The word is often used to refer to political contests, but it can be applied to any type of close competitive event, from a nail biting game show to a presidential campaign. It’s easy to lose sight of the real issues at stake in a presidential horse race, with all the mud-slinging, name calling and attack ads.

Historically, horse races were organized by colonial governors and settlers as a way to promote the colonies and attract tourists. Then, in the 19th century, speed became more important, and thoroughbreds were bred to be fast. Today, the sport is dominated by the United States, which is home to six of the world’s ten largest racing tracks.

In addition to the prize money, a race’s success depends on how many bettors turn out and what the betting market looks like that day. The bigger the fields, the higher the odds, which make it more difficult for a long shot to win. To draw bettors, race organizers must offer big purses — the total amount of money to be won. That means a lot of people will have to try to beat the favorite and take home some of the bounty.

Many bettors are regulars at the track and know their horses by name. But even casual visitors can pick a favorite in a race. They might cheer a horse by its number, or, as with Seabiscuit, call out “Come on, Number Three!”

Before a race, trainers will often walk their horses in the walking ring to see how they feel. If their coats look bright and rippling with just the right amount of sweat, they’re believed to be ready to run. That was the case with Mongolian Groom, which seemed healthy enough when it went to the starting gate.

Once a horse begins running, it may be given drugs to mask pain and help the animal perform. For decades, nearly every thoroughbred has been injected with Lasix, which is marked on the racing form with a boldface “L.” The drug’s diuretic function prevents exercise-induced pulmonary bleeding, a condition that occurs when a horse pushes itself too hard and can be deadly.

Another common medication is Adequan, which is a brand of polysulfated glycosaminoglycan, an ingredient found in joint supplements for humans and dogs. But its use is controversial because it can be abused by trainers to illegally enhance a horse’s performance. It can also be fatal to a horse that is already too tired or injured. The federal government has prosecuted more than 30 trainers, veterinarians and drug salespeople for abetting on horse races. Those in charge of ensuring that horses are sound before they enter the ring have been roused from their torpor by the scandal.