I tend to think that Biden, Sanders, and Warren all get a dip in the polls, whereas Gillibrand and Harris both strengthen their positions. I do think 18% is probably pretty close to where Gillibrand starts the primary season, she’s a compromise between the establishment and progressive wings, and has lead the charge on the issue of sexual assault for years. I think Booker takes the more establishment wing, as well as in the south. His primary base would be the mid Atlantic, and would be a great VP option. I think Harris has some strength in the West and south, while also having the progressive and establishment support, due to her past as AG and consistency in opposition to Trump and support of progressivism. I think McAullife will have strength in VA, but not much outside of that, due to the field already being large and split. Klobuchar is one to watch, as she could be strong in the Midwest and may be positioning herself as a more moderate voice, though I’d keep her support in the low single digits. HRC won’t run, but would poll around 7-10% tops.
In terms of matchups, I think democrats retain a generic ballot lead of 7-9% against Trump. Biden polls about 47-38 against Trump, with strength in the Midwest. I think Sanders is probably around the same. Gillibrand gets 46-37, Harris 45-39, Booker 45-37, and McAullife gets 42-36. I think HRC would poll 42-38 against Trump, with basically the same electoral map as 2016.