I don't think it's a secret that part of Kamala Harris's strength is her appeal to Black voters -- many of whom were dubious about Biden specifically because of his Gaza policy. Especially in Black churches, there has been increasing call for more active involvement in peacemaking by the US. It seems unlikely that a staunch pro-war stance would shake her support that much, but it also seems a way to activate voters who were considering not voting at all in November.
https://thehill.com/homenews/campaign/4677821-biden-risks-losing-black-voters-over-gaza/