Thanks for posting Sheldor...Jon in conf relates what happened but I don't believe that he really thinks it was an accident...I transcribed the scene a little differently...

At night after returning from TC, see a snake in the tree... see Jaclyn, Missy, Natlalie and Baylor...
Jac: so what happened,
Missy: I don’t know
Jac: Did Alec vote for himself?
Natalie: No....didn’t you tell me that me, you and ...Jaclyn finishes her sentence: Jon are voting Keith.
Natalie: I thought me, you, and him were voting Alec.
Jac: Oh...
See Natalie...
Natalie in conf: Just the way tribal went, I knew I had to pretend to mess up and accidentally vote out Alec instead of Keith, and
See Jon up close
Nat: ....and act my ##### off to convince them that it was a mistake
See the girls talking again...
Natalie to the girls: You’re the only one who talked to me. Came up to me for two seconds. I didn’t talk to anyone else .
Natalie in conf: It was a risk I was willing to take because I just didn’t want Jon to have more power, (Close up of Jon) in this game than me.
Natalie continues to Jon: I thought she said me, you and her were voting Alec...
See Keith by the shelter
Jon: No
Nat in conf: I think I sold it to them properly, but, Jon is on my hit list. He’s been on my hit list since he sent Jeremy home, so it’s been a long time coming, I need to make some moves soon (hear dramatic music playing with faster paced tempo), then back to the huddle at night with the 5:
Natalie: Nobody was talking to me. Nobody checked in with me.
Jon: I know, I know, but....
Zoom in on Baylor as Jon says: So, you got it mixed up. It’s all good.
Jac: that’s fine
JOn: no big deal
Baylor in conf: It’s hilarious watching Natalie be an actress toward Jon and Jac tonight, because if they were smart they would know that Natalie knew exactly what she was doing...
cut back to the group,
Jon to Natalie: That’s fine
Jon conf: At tribal there was a little bit of a debacle, I guess we didn’t talk enough going into it, and Natalie didn’t fully understand who to vote for. It’s unfortunate that it happened here because Keith really is a threat to win immunity challenges.
See Keith sleeping in the shelter
Jon continues conf: That’s a big, big deal. That potentially could screw up a LOT of plans.

With the big blindside tout, it really seems apparent to me that it will either be Natalie or Jon that gets blindsided.