There is no witness like a hostile witness. When it comes to Christianity, Bert Ehrman is pretty hostile but he is a historian and he makes a pretty good case for the historical existence of Jesus (whatever you make of Him):

I don’t agree with how Ehrman processes the evidence (obviously); there are solid reasons for differences in the gospels and other things he mentions. I had to smile at the way the interviewer pushes back because Erhman is using the same approach apologists do. As if that in itself makes the facts wrong. The interviewer tries to resort to the same old “yeahbuts” but Ehrman is honest enough to point out that that particular emperor will be ill-attired for the coming winter months. He’s naked. Which is to say, those arguments play well to the sympathetic crowd but they don’t really work.

In the end Ehrman makes the point that you can’t look at the historical facts and say Jesus didn’t exist. So you’re not left with “Was he?” but rather “Who was he?” Once the point that Jesus existed is established there is a case to be made about who he is.