In Ohio, for example, Republicans look likely to get round to supporting repeal—significant in a state with 141 prisoners on death row.

破折号比逗号更加醒目，其实这里用逗号也可。

形容词短语 significant in a state with 141 prisoners on death row，相当于一个非限制性定语从句，描述前文整个句子内容。意思是，这（前面说的情况）在一个有141名囚犯被判死刑的州里，意义是重大的。

In Ohio, for example, Republicans look likely to get round to supporting repeal—which is significant in a state with 141 prisoners on death row.

In Ohio, for example, Republicans look likely to get round to supporting repeal，which is significant in a state with 141 prisoners on death row.