Trump has changed his tone and his position during the campaign. He used to claim that Obama was born outside of the United States. Now he says he believes that he was born in the United States. When a candidate changes their position, the people voting should be allowed to change their opinions, too.
No, former GOP primary candidates who don't support Trump should not be banned from running for president again because our country is a democracy where the people get to choose. One party should not dictate the rules. The people should be able to vote for whichever candidate they want; therefore, everyone should be able to run.
Those that ran in the GOP primary for president who have chosen not to support Donald Trump should be given another chance to run again. In fact, it is admirable that they are putting the country ahead of party politics. This may not endear them to the establishment, but should be favorable in a future run.
It doesn't matter if the person is a member of the GOP or a former primary candidate, anyone should be allowed to say that they do not support Trump. I don't think that belonging to a party should mean that a person cannot express their views regarding a presidential nominee, there is no room for curtailing such views in America.