If we're looking for a more recent historical of a longshot candidate starting his campaign very early, it would be Carter. But it wasn't that early and, for all "Jimmy Who?" jokes Carter was far more prominent than Delaney.
I don't think a candidate needs to be well known right now. That's not really that important. Heck, almost all of the likely candidates are obscure. You really think the average voter knows who Kirsten Gillibrand is?
But what you do need is a plausible means by which you can escape from obscurity. While we've razzed on Beet for thinking that Tulsi Gabbard will win the nomination, I do think he's at least right in thinking that if Gabbard were to run, she'd have a clear path towards escaping from obscurity (combination of her age, gender, race, religion, and her....uh....provocative foreign policy statements would combine to get her a healthy dose of media attention). That wouldn't win her the nomination, but it would get her noticed. Heck, even a Seth Moulton I can see escaping from obscurity.
But Delaney? I'm unclear on what he would realisitically do that would get anyone to pay attention to him. He is just a boring, conventional, moderate-ish Dem. who's a backbencher in the House, who is also boring from both a biographical and demographic standpoint.