The bitter truth for Palestine is that Israel/Palestine is not a security issue for USA.
What happens there will not have any influence on Americans in general.
Although Gaza is an obvious humanitarian problem, USA has obligated itself to protect Israel by law many years ago, when the exact same humanitarian issue was the case but with Israel as the victim.
AFAIK favorability for helping Palestine is about as high as for helping Israel, so this is not about which standpoint has the most votes, it’s simply not an important issue for the American election.
Ukraine is not mentioned much either, and that is an actual security issue for USA, and especially for its NATO allies, and has way higher support (AFAIK) than Palestine.
So it’s not because Democrats are afraid, it’s just not something they choose to become an important issue for the election. As heartbreaking as it may be, other issues are considered more important for Americans.
That said, I have no doubt that Harris will put way harder pressure on Israel, I think she recognizes the hardship of an oppressed minority.