[GOPJ]

The guy who did the poll talked with Chuck Todd on his afternoon show... He said he CHANGED the people he was polling by ADDING 10% who said they were "VERY CONSERVATIVE'....

In short he added Cruz voters.

It would be as if a dem added 10% MORE people under age 30... that would boost Sanders numbers.

[okie01]

You've just been introduced to how a pollster adjusts his polling sample to replicate what he believes will be the actual turnout.

"Very conservative" voters are relatively difficult to poll -- as a group, they don't answer unknown phone numbers or respond to pollsters. As a consequence, unadjusted polling samples tend to under-represent them.

Moreover, the Republican primary party polling to date further suggests that "very conservative" voters are turning out in a higher proportion than expected (see Iowa).

Under these circumstances, the pollster has re-adjusted his polling sample to represent what he believes the actual turnout will be.

[jennychase]

10% is big weightage swing. Now if you add 10% Cruz voter and reduce surge factor, one can swing towards Cruz. Even with skewed data, both are within error.
It means Trumps numbers are way high, around 39-40