It is not that they are inaccurate (which they are), it is that they will poll RP low because of who they poll. So a rise in the polls by RP mean that in the limited scope which they poll RP has gained. So it is inaccurate but among the group polled "likely Repub voters" he is increasing. I believe RP has tremendous "not likely Repub voters". So if you take the poll numbers and add the others, it is good that RP is polling higher, although they aren't accurate.