An independent could win the Presidency. Donald Trump was as close to being an independent as one is likely to get though.
The Democrat Party has evolved since the Clintons of 1992 to a moribund condition. An independent that could disentangle ecospheric issues from moral issues such that ecosphere reform is without immorality preconditions (how does homosexuality, recreational drugs or abortion actually have any relevance to global warming?) could get some votes from people somewhat disgusted with matters of immorality the Supreme Court decides eventually anyway.
An independent would probably need to be a billionaire or someone with tremendous resources able to buy advertising without party contributions and with the media likely against them. If the candidate isn’t actually very different politically from the party candidates whats the point though?
Probably an independent candidate would have a position equivalent to an independent primary party that merges to take over the mainstream party to run as the party candidate. President Trump worked something like that. So a candidate with numerous independent ideas could present them and try to get enough support to get delegates for the national convention and the nomination eventually.
Usually regular candidates try to present a formula for a platform appealing to enough voters to get a nomination instead of leading with new and independent ideas that attract enough voters that recognize the reason and utility of the ideas.
A candidate that has ideas about reforming capitalism and environmental economics, securing the borders, renewing the environment and eliminating poverty could draw voters from all parties. The trouble is that the people that run require tons of money just to start.
There is also the problem of brownie point qualifications. Candidates need to have a PhD in Environmental economics, be as svelte as a decathalete, rugged as Chuck Norris and have graduated from West Point with a Silver Star from Thermopylae, the Croix de Guerre with clusters and be a Mister Rogers Bible instructor who gives blood twice a week while serving food to the homeless at a leprosarium.