Potentially relevant re: Warren's future presidential intentions:
https://twitter.com/HotlineJosh/status/1294054174859186177
Unclear if this was just spin to help her land the job, or alternatively if this was specific to a scenario in which Biden wins this year. But if serious, it sounds like, even if Trump wins this time and there's an open Dem. contest again in 2024, Warren might not run.
Perhaps she's acknowledging where she is in her political career? Makes sense: one of the things I've always admired the most about her is how she always seems to know who she is & where she can be the most helpful; she's also so completely honest.
As somebody who planned on being a supporter of hers in her next run, though, I'm saddened but nevertheless accept it. 
I hope she's more able to enjoy Bailey & her family life.
That would be my guess. I hate to say because I'm a fan of her as well, but she did recently turn 71 and will be 75 on Inauguration Day 2025. That fact alone may be playing into her thinking regarding a second run. Especially if Biden pulls off two terms contrary to conventional wisdom.
