It’s pretty easy to figure out the probability of 6 successful coin flips in a row. For simplicity, let’s say heads is for Hillary, tails for Bernie. Assuming a fair coin (I know, I know) there is a 50 % probability of getting a head on each flip, i.e., 1 chance in 2.
Number of flips===========Probability of successive heads
1=====================1/2
2=====================1/4
3=====================1/8
4=====================1/16
5=====================1/32
6=====================1/64
So, there is 1 chance in 64 of getting 6 heads in a row (or successfully calling 6 coin flips in a row.)
1/64= .015625, or 1.5625%. Unlikely, but not impossible.