虚拟语气，与过去事实相反 : 从句 :had + 过去分词 主句 :would⼀ should⼀ could⼀ might + have + done

虚拟语气,实际上,它从未发生过.
被动语态:would/should/could/might +have + been +done
Politician would have been elected out of office 被动语态（政治家"被"赶下台）,不是自愿下台
Politician would have elected out of office 政治家选择自愿下台

would have been done 此处是过去将来完成时（少用） ...
Countless divorced politicians would have been elected out of office years ago，几年前，很多政客都一定会被赶下台
let alone gotten one，更不要说离一次婚（真的离婚），这里的one指代的是前面的紧挨着的divorce，离婚

整合起来：几年前，要是那些个离了婚的政客有离婚的念头，就一样会被赶下台，更不要说真离婚了。

这里的虚拟语气是虚拟语气的倒装：略去条件句中的if，将had 前置，直接引出虚拟条件句。

这是与过去事实相反的虚拟语气，其中，if条件从句倒装了（倒装的原则是：如果if从句中有助动词were, should和had，可以将if省略，把were, should和had提前）。
这个句子转换成正常的语序就好理解了：If they had even thought of a divorce, countless divorced politicians would have been elected out of office years ago. Let alone gotten one.
其中 would have been done 实际上就是与过去事实相反的主句（:would/ should/ could/ might + have + done）结构的被动语态（被赶下台）。

此处的would have been done是过去将来完成时 ，在初中范围内不会用到，would是will的过去式，have been done 是完成时的标志

虚拟语气不仅有主动+谓语，被动+谓语也是。