If the deplorables comment was the second biggest misstep of her campaign, backing down from it was the biggest. The comment was valid in it's full context, even though it was politically tone-deaf. A large chunk of Trump supporters really are deplorable. Backing down or "going high" is what made it into such a massive vulnerability.

As an aside, Democrats have a lot to answer for in how we got to a culture that generates so many deplorable people.