They are playing a propaganda game. By continuing these false polls, they hope to discourage his voters from coming out, discourage campaign contributions, and lend an air of legitimacy to what will undoubtedly be an attempt to stuff the ballot boxes in Democrat controlled voting districts in the urban centers in November.
The perceived popularity of a candidate is one of the non-rational reasons the dumbest 10% of voters choose to vote one way or another or not to vote at all. Supposedly the 10% of folks who are the swing voters decide all national elections based on how they are swayed, and they are swayed by things like personal appearance of a candidate, debate skill/flubs and how popular one or the other seems.
Freegards