Why is an uncontested lead an advantage in a horse race?

Racing commentaries often refer to the fact that a front-running horse was allowed an uncontested lead, which can sometimes, but not always, prove to be an advantage. Lack of competition for the lead allows a front-runner to dictate its own fractions, without setting too frenetic a pace and, thereby, expending too much energy.

 

Obviously, every racehorse has limitations to its speed and stamina. Most can maintain top speed for two furlongs or so, but no further, which is why front-runners who set off ‘lickety split’ at the start of a race – either by their own volition, or because they are ‘harried’ for the lead – often fade out of contention when the race begins in earnest.

Conversely, if a front-runner is allowed to take the field along at moderate, or even slow, pace, it will be able to maintain its effort for longer. If a front-runner can maintain, or quicken, its speed, such that it covers the last two furlongs of a race in, say, 24 seconds, it stands to reason that a horse that is a few lengths off the pace must cover the distance in, say, half a second faster in order to win.