Nowadays, in the hyper-tension of the 18 month long "primaries" to the '16 election, I think I should preface my US-centric political posts by saying that I'm Canadian, not a US citizen. I like it being a Canadian, but I'm not very enthused about Stephen Harper, who I'm quite sure will be ousted by a minority coalition of Liberals and New Democrats before end Oct., 2015. Note that timeline, "before end Oct. 2015", so in about 1/2 year's time. In Canada the election campaigning hasn't begun, yet, it's so low key and short. Very different than in the US. So I figure that Harper will be gone, shortly, and I'll be helping to ensure that result in every way possible.
Now to US politics: Hillary Clinton will not drop out of the race. Not for *any* reason. In '08 she hung on way past the point where people were laughing.
I don't know what Warren will do, but she *did* sign that letter from the 15 women Dem Senators asking Hillary Clinton to run. On the one hand it would've been churlish to not sign on, when asked, but on the other hand... well, she did. And there's no way that Warren can plead even the slightest degree of ignorance regarding what Hillary Clinton stands for.
Warren's history of identifying as Republican well into maturity and into the Reagan years tells me that she's coming from a very different place than I do. Now I'm happy that I can repeat that I'm Canadian so I don't have any innate "lived it" understanding of US bipolar politics. As a youth of the same age, but living in Canada, I came into the Reagan years after experiencing Pierre Trudeau, and before him Lester Pearson, and so I come from a totally different and more pacifistic political culture.