There a problem there which is that the majority of the population is "left". If you actually have policies that will improve their lives they will vote for you. Kamala is trying to get a small number of republicans while throwing away a majority of the population. She is trying to be the center of the establishment rather than at the center of the population.
"Hardline leftists" are the majority of the population.
Kamala shouldn't go after some fictional middle that doesn't exist. She should go after popular policies that the majority of the population wants and just not care what they are called.