General Discussion

And my pick of who I think is most likely to win a primary. She has been my likely pick for months.

Why?

Some reasons focus on electoral math, some on society and some on issues (in no particular order).

Electoral math: CA moved it’s primary to March. Senator Harris was a popular AG and won her Senate election by double digits and polls solid positive numbers in CA. She is the clear favorite. Even with all other things being equal, she will be the only candidate from CA on the ballot and has every advantage going into that race there. I also think that such a well attended, well received speech, so early in cycle, may thin the field a little and improve the calculus for success.
Making it to the general with strength will allow her to focus on the Midwest (specifically OH, MI and WI) and PA, FL, NC and VA. She will grab the northeast and west coast will little effort (oversimplifying a little for brevity).

Society: being a middle-aged women of color will be a benefit in this environment. Not to old, not to young. A women and a PoC will draw a sharp contrast to anything republicans can put up (my assumption being that trump will not be their actual candidate in 2020, as that seems more unlikely with each passing day).
I think a younger professional women of color is touching on the need for change, in both perspective and appearance that will bring both women, young people and POC to her banner in a general election that no republican could even dream about getting.

Issues: from institutional racism to healthcare, she touches on the issues that people want and need to hear from a candidate right now. Her focus has been on things like Medicare for all, education and training for an economy far more automated and global than any in history. Addressing climate change as an emergency and moving to a green economy. Finally, the cost of college and student loan debt. These are my issues that I care the most about and weigh heavily on my decision to support a candidate. The ideas have to make sense and have real potential to make real progress and most importantly, I need to not just believe they will make real effort on these things but know they will make those changes happen. Senator Harris is sincere in these objectives and wants to make real progressive ideals into a reality.

Sorry it was so long but I wanted to articulate it as best as I could.