The expression "hands down."

How did the expression "hands down" come to mean "without a doubt?"

The phrase hands down comes from horse racing, as explained by The Phrase Finder:

Jockeys need to keep a tight rein in order to encourage their horse to run. Anyone who is so far ahead that he can afford to slacken off and still win he can drop his hands and loosen the reins - hence winning 'hands down'.

And confirmed by Etymonline:

To win something hands down (1867) is from horse racing, from a jockey's gesture of letting the reins go loose in an easy victory.

I found this antedating of the phrase from The New Sporting Magazine, 1855:

And I found examples of the phrase being used figuratively in other contests by the early 1880s.

Meaning

Win easily, with little effort.

Origin

Jockeys need to keep a tight rein in order to encourage their horse to run. Anyone who is so far ahead that he can afford to slacken off and still win he can drop his hands and loosen the reins - hence winning 'hands down'. This is recorded from the mid 19th century. For example, 'Pips' Lyrics & Lays, 1867:

"There were good horses in those days, as he can well recall, But Barker upon Elepoo, hands down, shot by them all."

It began to be used in a figurative sense, to denote an easy win in other contexts, from the early 20th century.

(Source: http://www.phrases.org.uk/meanings/win-hands-down.html)