Has Warren ever demonstrated that she would be a good president? She has fairly narrow expertise -- all of which is more useful in Congress. I've seen about 200 articles about Warren running and none about how well she would handle foreign policy and a host of other issues with which she has very little experience.

And sure, a president doesn't need to (and can't) be a policy polymath, but Warren is pretty close to single-issue. I thought the left had learned from its (self-pronounced) mistake with Obama, who had no "CEO" background. He was elected because he fit the moment, not because he would be a good president. I think he's turned out fine (different conversation), but many liberals disagree. Elizabeth Warren would never be elected, but if she ran it would be to ... fit the moment. Not because she's qualified.

Addressing mk's point -- yes, Warren could raise the stakes, adjust the debate, for Hillary if she ran in the primary. But a) that wouldn't help Hillary's chances in the general, if you care, and b) nothing that is said, promised or discussed in the primary has any bearing on policy after the inauguration.