The better question is where does the term Republican or Democrat occur in the constitution?
You refuse to answer the first question. The answer is Delegate is nonexistent. Delegate is fraud.
At least you admit ignorance of the Constitution by avoiding with another question. Nobody understands Constitutional Elections because the Article clause was twice written and Amendment 12 is still gravely flawed.
But to answer question 2 Government MUST make a list of all persons. Republican is not a person. What is his first name? Is Republican his last name?
Even worse the party brand BANS other persons.
If I find time, I will write a book on U.S. Elections, and maybe even write a future Amendment to the U.S. Constitution. Why not, 250 years later, 100s millions people and the clause is still flawed. That many people cannot write 2 coherent paragraphs.
But consider this, pretty much ...
Everything everybody knows about elections is false. :-)