toss hat into the ring
toss (one's) hat in(to) the ring
To announce or make known one's intention to compete against others for something, especially in a political race. After Arnold Schwarzenegger was elected governor of California, it seemed like all sorts of celebrities tried tossing their hats in the ring.
toss one's hat into the ringand throw one's hat in the ring
Fig. to announce that one is running for an elective office. Jane wanted to run for treasurer, so she tossed her hat into the ring. I won't throw my hat into the ring until the last minute.