back the wrong horse

Make a wrong guess about a future outcome. The term comes from horse racing and is occasionally put as bet on the wrong horse,and has been used in this context since the late seventeenth century. It has long been applied to other situations, especially politics, where it means supporting a candidate who loses. Charles L. Graves used it in Punch’s Historyn(1922): “Lord Salisbury made his remarkable speech about our having backed the wrong horse, i.e. Turkey in the Crimean War.”