https://www.theguardian.com/world/2017/oct/29/mexico-corruption-pri-santiago-nieto Please develop a summary and commentary on this news article.

https://www.theguardian.com/world/2017/oct/29/mexico-corruption-pri-santiago-nieto

Please develop a summary and commentary on this news article. It should briefly describe what the story is about and offer some analysis on its overall political significance, focusing mostly on Mexico. It should be a couple of paragraphs long, thank you.