Rand now at 3rd...
Voted.
You mean they can be disqualified for candidacy for engaging a Democrat in a debate before the nominee is chosen?Debates have to be sanctioned by the RNC.
Technically speaking though, I think they could have a debate on the senate floor. If either of them captures the floor and they then yield it to each other in order to debate each other... Sound good in theory but my guess is the media would start blaming them both for 'using up valuable senate time'.