I think it's silly to have these debates, months before anyone's going to get serious about picking a nominee to run for president, with ten candidates. No one has any time to say anything…which is okay because no one has much to say now.
However, if we're going to have them, there's a question that I think should be asked, and it should be asked at both Democratic and Republican debates. It would go roughly like this: "Is there any other candidate on this stage that you would hesitate to support if he or she secured the nomination of your party? And if so, who and why?"