I'm not going to call bullsh*t on Warren's ancestry entirely here. It's a very cultural thing in Oklahoma for pasty white people to claim to be Native American when they are like 1/168th Cherokee or something. To her credit, it seems that Warren merely claimed to have Native American heritage, which makes her a lot less annoying than most other "Plastic Natives". However, was this relevant to bring up in a Massachusetts Senate Primary? Most likely not.
She used her "heritage" to con her way into the club of tenured Harvard Law Professors.