one-horse race
noun [ C usually singular ] uk/ˌwʌn.hɔːs ˈreɪs/ us/ˌwʌn.hɔːrs ˈreɪs/
只有一位参赛者有机会获胜的比赛，一位参赛者遥遥领先的比赛
a race or competition that only one of the competitors has a real chance of winning
This election has been a one-horse race right from the start. 这场竞选从一开始就是一场一人稳操胜券的竞赛。