There is no significant leftist movement or momentum in the United States. None. Your choice is between far right (Republican) and center right (Democrat). Both are (neo)liberals. Both are capitalists. Both are united when it comes to US foreign policy. As of the last election, both parties are pro-death penalty (it opposition to the death penalty dropped from the Democratic Party Platform in the 2024 election). Both support the current private health insurance system that most people are angry about.
Notably, Tim Walz (VP candidate) praised UHC in a press comment after the shooting: "a terrible loss for the business and health care community", "Minnesota is sending our prayers to Brian's family and the UnitedHealthcare team". Amy Klobuchar said: "My thoughts are with Brian Thompson's family and loved ones and all those working at United Healthcare in Minnesota". So Democratic Party leaders were very much big supporters of these health insurance companies.
https://www.kff.org/private-insurance/poll-finding/kff-surve...