challenger

1. N-COUNT A challenger is someone who competes with you for a position or title that you already have, for example being a sports champion or a political leader. 挑战者

The strongest challenger, Texas Democrat Martin Frost, has withdrawn from the race. 最强劲的挑战者，德克萨斯州的民主党人马丁·弗罗斯特已经退出了竞选。