If Republicans or Democrats invented a person using only digital footage to pretend they were real, could they get their creation to win their party's nomination for President?

Probably not. That person would have to meet with the higher ups that make the final decision.
Remember, just appearing on TV means nothing. Americans do not vote on who to be president. Their vote means nothing.

I could see the republican party nominating a corporation.

maybe i didnt say it right.

my hypothetical situation is that the higher ups in the party are the ones behind creating this fake persona to win the election for them.

This. Lmao

No. We have to remember that candidates still have debates. A real-life-person candidate couldn't debate against a TV screen. That'd be a dead giveaway.

I'd vote for Max Headroom.