Now that Paul is in bye-bye land, it now looks like it has boiled down to a tossup between Craig and Nicole. Each has many clues pointing toward them. Both have been the cause of the team losing money: in ep 1 both Craig and Nicole failed to grab the bag; in ep 2 both were on the soccer playing group which lost out to Mark and Kristian and lost money for the pot; in ep 3 Craig talked after the finish line and cost the pot $10,000 and Nicole conned Alex to name the green apple twice and lost the pot $12,000. And so it goes. In the last several tasks both Craig and Nicole were on the same losing group so either one or both of them could be sabotaging the task. Hard to say.
But other clues seem to point more to Nicole than Craig. (1) in the opening titles before the title "Mole" is seen, the letters spell out "MOM", which did not refer to either Marcie or Liz but may refer to Nicole who as a OBGYN Doctor works with Moms or Moms-to-be. (2) References to apples may refer to "an apple a day, keeps the doctor (Nicole) away. (3) an arrow in ep 7 quiz points to the answer "3" which was identified as Nicole. (4)The sign on the wine barrel in ep 5 "N2O" could refer to Nitrous Oxide a gas used by doctors for the Laparoscopic management of the persistent adnexal mass in pregnancy. (5) Nicole is hit first in the paintball fight and keeps $10,000 out of the pot.
Also note that at the dinner in eps 5 and 6 everyone except Nicole is dressed in black so that she stands out from the rest and therefore is different from the rest. As the mole is different from the rest.
She also in ep 8 is first to call out a cell number. The producers in "private meetings" with the mole often advise the mole of what is coming up and what they should do; such as call out a particular number or team they want to be on since the mole knows the significance of that call. Such as which cell would not have an exemption and would give the mole a chance to lose money for the pot. Nicole was alone outside the cabin and on the beach in ep 1; in the last few eps she has had a room by herself (we all think, at least) since she is the only female left in the competition. These are perfect times for the producers to sit down and plan for the next day's action and what group she should be on. They tell her what group has the best chance to lose or not make money for the pot and then note that in almost every case Nicole is the first to call out her choice of groups.
Look at many of the tasks Nicole is on (for which she is quick to chose a group, a group with a better chance to sabotage the game) and she slows things downs, gives the wrong answers, or counts wrong.
There is too much evidence for Nicole not to be the mole.
And still Paul thought Craig was the mole, he was electrocuted so Craig is not the mole, and Mark has been too good at winning money for the pot to be the mole, that leaves Frau Doktor Professor Nicole as the MOLE.