I don't think you get it.
Infidelity and prostitution is not "an issue" for me, as far as politics, but it normally is for many. My problem is: If the person you hired to fix your car obtained that position due to sleeping with somebody, would you feel comfortable about it? How about your doctor, the local police chief, etc.? This is the top job in the country, if not the world. Given Biden's age, if he wins in Nov., Harris could very well be in the presidential office before his term is up.
If she'd actually been a prostitute for a while, to make ends meet, this would not bother me that much. The fact that she whored herself out to a powerful, older, Democrat, as the first move in her political career, reveals more about her character than her words on TV or her political career in California. It completely dismantles any supposition of ethics that I'd normally give a candidate.