The reason the right has been able to push Christo-Nationalism into the highest levels of government is because they started small 50 years ago. You can't just plop radical in the highest office and expect anything big to change. You need to slowly fill in the lower ranks and brainwash constituents at a local level until the process naturally begins to favor trumpian candidates, at which point a dictator is bound to eventually emerge with the full, unwavering support of a large chunk of the populous. The American left is half a century behind the fascists. It's not about any one candidate, it's about altering the political ecosystem to make it more favorable to your ideology.

Local voting is how you get change in general to happen. The federal government is setup to resist change. The local governments aren't. If you want a young Presidential candidate in a decade or two, find a 20-25 year old you trust to be mayor now, and then either a state level senator, or governor.