Trump ran to the left of Hillary Clinton as an anti establishment candidate in many key issues.
If the democrats field someone that isn't anti establishment then Trump will get smashed. Because the longer he is in the more obvious he is a red Obama, no different to the rest in pushing for the wealthy, empire and big business. The irony outside of Rand Paul all the other republicans are bigger wannabee war criminals like Rubio.
You guys can bag out AOC because she doesn't give a lot of consistency and says things that don't resonate with you but they can resonate with many Americans who feel disenfranchised. The fact she came out of nowhere to beat an establishment corporate Democrat leader and the amount of verbal attacks you, the corporate left and right, and the lame stream media give is a good indicator she does offers Trump meaningful competition (you can't even see its Trump like in reverse how its boosts her popularity the more you attack her).
I want Tulsi to win because I believe she can unite elements of the left and right and is firmly no controlled candidate of the establishment. But it is wishful thinking.