Dubuque, Iowa CNN  — 

Donald Trump uses Twitter to speak, to poke and to retweet.

And his penchant for public musing has turned into a key element of his campaign – allowing him to steer public debate and train attention on whatever issue, or chosen enemy, he desires.

So what’s in a retweet?

That’s one of the questions he was asked in an explosive news conference centered mostly on immigration in Iowa Tuesday. But Trump also shared his Twitter philosophy in response to reporters’ questions.

Reporter: Can you tell us your retweet strategy? Do you endorse what you retweet?