No one can explain to me why they think she cant win.... .I am curious about your answer?
She's too one-dimensional in a lot of ways. We know her foreign policy and security philosophy, but haven't got a clue what her tax policy, economic policy, social policy, or position on social security or medicare might be. Those things are as important or more so than security to the average American.
Add that to the fact that she's a black woman, and the fact that neither major party has ever nominated either a black or a woman for President, because whether you like it or not, those factors impact the way voters vote. Of course, that wouldn't deter me from voting for her if she were nominated, but I would be nervous about her chances of winning, if I were to have to choose in the primary between her and someone equally good who did not have those handicaps.
As I said, though, I think she'd make a good President, and I would have no hesitance to support her for VP. It's the Presidential candidate that the voters vote for anyway, and I am quite certain that she could only help the ticket if she were in the no. 2 spot. She would definitely not be a drag on the ticket in the no. 2 spot.