There are ballot access deadlines and they will all be past soon. In Illinois the state law was just changed so that the President would be on the ballot as the nomination was going to take place after the original deadline had passed.
Of course there are deadlines. I am pointing out the depth (or lack thereof) of their effectiveness.
US Code, Title 3, Chapter 1 <--PRESIDENTIAL ELECTIONS AND VACANCIES
Here is another good reference. I was looking for the Illinois statute (still haven't found a link to it), but this summary is pretty good ...
http://www.thegreenpapers.com/G00/Electors.html <-- Each state chooses electors
Here is, I think, the relevant part of Illionis law that bears on the subject of what names appear on the ballot ... notice that the naming of a person for the offices of President and Vice-President is OPTIONAL, but that the qualified party is on the ballot in any event.
The ballot shall contain no other names, except that in cases of electors for President and Vice-President of the United States, the names of the candidates for President and Vice-President may be added to the party designation ...
10 ILCS 5/ Election Code <-- Boring reading