1. Try the Trump/populist playbook on the topic: identify the problem, empathize, be mad, let them vent, but don't really focus on a solution.

2. Advocate austerity as a solution to inflation. Might be less economically ideal, but more politically viable.

edit to add: iow, Harris and other Dems could have thrown Biden under the bus a bit to try to avoid some of the blame. It's cold, and Biden directed an actually decent response to the supply-shock-driven inflation, but it'd be a kind of shrewdness like getting Biden to drop out that might have helped.