One can always point to a historical Jesus, because there were many in the first century according to historians like Josephus. So, it is always a safe bet to say (from a historical point of view) that Jesus existed. Otherwise, a serious historian has to reach for a mythicist theory, which is much more difficult to prove. But that doesn't mean that THE Jesus of the biblical stories existed, most probably not, what we have is the combination of many such characters.