This reminds me of a scheme for recounting ballots:
Recount until you achieve the desired result. Then stop and block all other recounts.
Here, the liberals take polls until they achieve their desired results, despite a high error margin and small sample.
Then they stop taking any more polls, keep repeating the desired results, and neglect to mention any other polls.
Perhaps the idea is: keep repeating it and some people will eventually believe it.
I wonder how much longer they can keep quoting the April Field Poll; it was taken before the Oracle scandal was publicized in all newspapers.