I am not sure what you want to know. States can not refuse to accept a constitutionally qualified candidate as president. Each state can pass state laws about how their presidential electors are chosen, so a state with a dominant political party could in theory effectively require that the candidate they vote for is acceptable to the dominant party and meets whatever qualifications they set up behind closed doors. States also set their own rules about whose names appear on the ballots, but these rules would have to be consistent and apply equally to all but it does keep a person with no money and no organization from having his name printed on the ballots and so does, in a way, add a restriction on who can run.
They are the people who are running for president.
Mitt Romney
Mitt Romney and Barack Obama
Candidates for President get to choose their own running mates.
Obama, McCain and Clinton.
The candidates up for election for the President of the United States in 2012 were current President Barack Obama and former Massachusetts Governor Mitt Romney.
President Obama's victory in 2012 will make future candidates consider using social media effectively.
Yes, the candidates running for president get to pick their own vice - president. After all, it has to be someone they get along well with.
The President selects his own running mate.
The Democratic incumbents Obama and Biden are running against Republicans Romney and Ryan in 2012.
Ralph Nader-Independent Bob Barr-libertartarion
Senator Bob Dole ran for President and his running mate was Jack Kemp, former pro quarterback and US Congressman.