0To "throw your hat in the ring" is an Americanism dating back to the early 19th century meaning to enter a contest, especially to declare your candidacy for political office. The "ring" in question was originally a boxing ring or other venue set up for fighting. Evidently it was the custom on the American frontier for a pugilist to literally throw his hat into the ring as a way of announcing that he was prepared to take on anyone in the crowd.
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