He hasn’t done anything dirty. Trump has tried to make Cruz *look* dirty because Trump cannot stand on his record, and that is the kind of person Trump is.
With no ideas or policy positions to share, Trump has to throw red meat to the media to keep the focus off his lack of understanding when it comes to governess or foreign policy.
You don’t think spreading the lie that Carson was dropping out of the race at the Iowa caucuses was dirty? Wow.