bet on the wrong horse：判断错误；做了错误的估计

e.g. To count on the small family farm as an important thing in the American future now looks like betting on the wrong horse.

现在看来，指望家庭小农场在未来的美国有所作为时估计错误。

e.g. He expected Bush to be elected President in 1991 but as it happened, he bet on the wrong horse.

他原指望1991年布什会当选总统，但结果他完全估计错了。