Aside from the usual lies about "cutting Social Security," the main thrust of the Democrats 2024 "campaign" is to convince America that Trump is, to put it mildly, a bad person. Orange Man Bad, so to speak.
They don't mention any of Trump's policies, because Americans are generally in favor of all of them. They cannot cite their own policies, because nobody would want them if fully exposed. On that front, they just lie about how wonderful the country is doing. And of course, they lie about Biden's failing mental health.
That's it: Orange Man Bad.