Throw your hat in the ring

To “throw your hat in the ring” means to announce your intention to enter a competition or election. This expression comes from boxing, where “throwing a hat in the ring” formerly indicated a challenge. Joe Biden did not hold public office after 2016, when he finished his second term as vice president and was in his mid-70s. So you can imagine the surprise when Joe Biden decided to “throw his hat in the ring,” or announced his candidacy, in 2019 ahead of the 2020 election. The senior student “threw her hat in the ring” for class president.