The flaw in thinking that not providing weapons to Israel will stop the slaughter of Palestinians is in the belief that nobody else in the world would be willing to provide support to Israel in exchange for what they bring to the table: friendly relationship with a powerful, high tech nation sitting at a major intersection of global trade.
The way the history of this conflict is told, especially in political circles, ignores that early in its history, Israel bought weapons from the Eastern bloc; it also ignores that there's is a large population of Israelis with Russian background; and it ignores that the fundamental policy change that must occur within Israeli society is making the quest to conquer Mandatory Palestine taboo. As long as the incentive of conquest exists (an incentive which, in the Israeli collective psyche, is fed by the notion that conquest <=> survival), Israel will continue buying/receiving weapons from WHEREVER. When it comes to their survival, they are agnostic.
What does that mean for the US? If we don't sell to them, China will; Russia will; India will. And for those countries, the returns in technological knowledge, trade favors, intelligence, growing regional influence will be worth it. So, you tell me: which presidential candidate can honestly hope to win on the message that they will purposefully decrease the US's ability to wield power AND increase American rivals' capabilities in the name of stopping a war that is not even at her doorstep?
None, because accusing a presidential candidate of wanting to weaken the nation is still a very potent campaign attack against them. I think Harris may handle Gaza a lot more urgency than Biden has shown, but asking her to place Gaza at the top of her agenda will open her up to attacks that are very difficult to fend off, especially if Israel starts making open moves towards the aforementioned rivals in the middle of the election season.
