damn, I just can't take it.. as Ass said, Kishi takes stuff that only happened in the fans minds and pushes them into the story... like Chidori being a lighttning jutsu.
I have the time now to go over all the points that make me think that way.

first time we see the chidori is in chapter 30, other than the name, it doesn't even remind electricity, not in form nor in it's effect on Haku's body.
next time, is in chapte 113, it's described as a stabbing jutsu, again, when we see the moment of impact, it doesn't have the slightest similiarity to lightnning. They practicly say that your hand becomes a blade, they don't even mention the word lighttning.
Again, at chapter 128, guess what, a cutting skill, not elemental.
chapter 146? no lighttning.
176? do you see any electricity currents in the water? becuase i sure don't... if it was a lightnning skill, then he probably would have electrified the water, right?
226? 227? 228? 232? Naruto eats a chidori to his chest there, and he doesn't seem shocked about it.


80 chapters later, in 308, Sasuke farts out the chidori shield, out of nothing, but it was never explained what actually does the damage. he just makes the air more "stabby"?
and actually, the chidori sword is almost normal, unless you think about the fact that it was later that you use wind elements to increase the cutting power, but heck, who cares. HxH did it much better anyway.

that was the last time we saw the chidori in action, so unless we count the chidori thing in 308, the jutsu never had the slightest resmblence to lighttning.

well, but my thoughts aside, Kishi decided that it's electricity based, so who am I to argue? I could as much argue about that Kakashi said that to merge two elements you need both hands (diffrent chackra from each hand) and said that Haku used Ice/WInd combo, even though he did single handed jutsus...