Others in ooposition had their moment where they ran against or disagreed with Trump.

Romney made it a spectacle which of course the media went nuts over and gave wide distribution. He personally attcked Trump:

Mitt Romney: Donald Trump is a 'phony, a fraud' - CNNPolitics.com

Romney should be brought to the fore and then dumped for Petraeus, who is better suited for the job in the first place.