Each choice should be read as "if X is the 2024 nominee, the Democratic party's chances of winning the 2028 presidential election are Y%", where X is the choice text and Y is the choice probability.
Conditional will be set by whoever comes out of the 2024 Democratic convention (nominally ending August 22) as the official nominee of that party. At that point I will N/A all other options and the nominee's option will remain open until market closes right before the 2028 election. Should the party's nominee change after the convention for any reason, that does not change the conditional (aka it is based on who they officially nominate, not who ends up running by the time November rolls around). I will not resolve the conditional based on any early virtual roll call or whatnot. Conditional resolves after the actual convention regardless of what happens beforehand.
Feel free to suggest other candidates for me to add if I missed some, though note that I don't plan to add anyone with a negligible chance (<0.5% or so) of being the nominee (to avoid clogging the answers).
Creator betting policy: I will bet in this market as any other.
How does this resolve if there is no election in 2028, or if the Democratic Party is prevented from participating in it?
Taking a plain reading of the question text, I come to the conclusion that in such a case:
If there is still a person who can plausibly be called the "Democratic candidate for president" (and is recognized as such by a preponderance of credible news sources) and they do not win the presidency in 2028 (which would presumably be the case if there is no election or if they cannot participate), I would resolve NO.
If there is no person who can plausibly be called the "Democratic candidate for president" in 2028, I would resolve N/A.
My prior for such a case occurring is sub-1%. If you believe strongly otherwise we should find an appropriate market and match limit orders. :D