Which may be why Trump under-polled in NH.
Cruz is Push Polling in South Carolina
There would have to be wide variance in both sample size and percentage to make a significant difference.
The weighted average for Trump’s RCP Average (29.5%) shown in the article is:
(.31*507)+(.31*725)+(.25*531)+(.31*395) = 637.12
507+725+531+395 = 2158
637.12 / 2158 = 0.29523633 = 29.5% rounded
RCP could be using weighted averaging. One would have to find an example with wide variances to verify.