With a quick one-over of the 14th Amendment, I am not sure if the Federal Supreme Court can even rule on him being on the ballot; it may be a state issue, and would be the federal government interfering in states rights.

On the other hand, the 14th Amendment makes pretty clear, unless 2/3rds of congress permit it, Trump cannot be president, and the US Supreme Court should be able to rule that he can’t be president, and it’s up to the states if they want to put someone on the ballot who can’t hold office (unless it is already ruled that someone that cannot hold the Presidency [such as anyone who was not born in the US] cannot be on the ballot, in which case, any such precedence should be upheld). If they are some how allowed on the ballot and win, they should not be allowed to hold office, and either their vice president should take office, or the winners political party if any should choose someone to hold office, or the Supreme court should rule the runner up (opposing democrat in this case) as the person to receive the next most votes should take office to respect the will of the people.

(to be clear, IF he is allowed to run and wins, but is not eligible for the office, who takes office in such situations should be decided by legislation passed by congress, and in lieu if of a law on file, the decision should fall to the Supreme court; which I highly doubt there is law on file already, and that the current congress is capable of passing any such legislation.)

A number of ways that goes, but without knowing deeper case law, that is my surface level interpretation of the 14th amendment.