Pushing her left after the election will work about as well as it did with Obama, Clinton, et al. unless there are some new strategies out there. But "left compared to Trump" is better than the alternative.

Biden has gone much further to the left on multiple domestic programs than expected from his previous record in part because of the successful pressure from the more left-of-center. You don't have to give up before you try.

Presidents get pushed to the left all the time. And to the right. A lot of it flies under the radar, but it happens constantly.