Harris has run an effective campaign under difficult circumstances. If she loses narrowly, I don’t think the left will put the responsibility on her shoulders; it is more likely they will blame Biden (for being a bad salesman), the MSM (for overstating our economic problems) and the voters (for being gullible enough to support Trump). As a result, Harris will remain the head of the realo faction of the party, albeit with competition from several blue state governors.
Having said that, Trump’s extreme policies are likely to push the party as a whole to the left. Sanders and Warren will be too old to run in 2028, so we will almost certainly see a new generation of fundi candidates calling for fundamental changes to the system, starting with the judiciary and the filibuster. The obvious choice, since she will be old enough to run for president in 2028, will be AOC.