I think Hauser is the real person. He went undercover into the Mars society with Melina and them, but ended up agreeing with their cause and joined them. Cohagen finds out, pulls him out, tries his best to wipe his memory, then sets him up with Lori to observe him and figure out the next move. That all goes south when Quaid goes to Recall and his mind merges all the realities. But throughout the confusion in his heart and mind, I think he remained closest to the revolutionary, reformed Hauser wanting to help the people of Mars, which is exactly what he did.
