Quote from trefoil:
We are here talking about a requirement that is in the Constitution, for the only Federal office that all 50 states get to vote on.
Whether a party qualifies to be on the ballot is a state matter. Whether a candidate is qualified to run for President is based on the requirements stated in the Constitution, because we are here talking about the only Federal office that is voted on by more than one state, and the only one for which the requirements are specifically and clearly stated in the Constitution.
Therefore, the question before us here, whether Obama is over 35, and a natural born citizen of the US, is a question for Federal, not state, law. The question of whether the Democratic Party can appear on a ballot is a question for state law only.
States are sovereign only on questions that pertain to their level. The Federal gov't can't tell a state gov't to put the Democratic Party, or any other party, on the ballot. It can tell a state that it has to send its electors to the Electoral College for a particular candidate if that candidate meets the Constitutional requirements and has qualified under that state's laws as that state's candidate for the Presidency.
There is no Constitutional mandate for how that candidate is chosen. By custom, the candidate is chosen by statewide popular vote. Some states, like Maine, divide it up by Congressional district. From the Constitution's POV, all this is fine, because it does not state how the state's candidate is chosen. It does very particularly state which citizens are eligible to be President, however, and it also states that each state must recognize all the other states' certifications on a person's citizenship status.
Since Obama is over 35 and no one is disputing that, the only thing left is his citizenship status. That status has been certified by Hawaii. End of story.
Before the 2012 elections at least 5 states will have laws making it necessary for each presidential candidate to present proper documentation verifying constitutional eligibility to the Secretary of the respected State before they will be allowed on the state's ballot.