The odds of any single flip turning up heads is 50%. And, probability says that, over a long number of flips, half will be heads and half tails. But, the odds of six flips being the same are 0.5^6 (or 0.5 x 0.5 x 0.5 x 0.5 x 0.5 x 0.5) = 0.0156 or 1.56% (not impossible, but pretty unlikely).
But did Bernie call heads overtime?