Why is that poll bogus?
Because it is not represenative of the political landscape of our country. Not even close.
It is only the November election results that will constitute a valid polling of the American public (and whatever alien/dead votes the Democrats are able to garner) and this will still be a poll confined to a sampling of ACTUAL VOTERS. There will be many people that will not vote (for whatever reason) and will not be represented in the poll.
All these polls in the run up to the election have great potential for fraudulent interpretation or accidental skewing of the true feelings of those sampled. The way the question is asked, who is asked, when they are asked...all have bearing on the poll results. Politicians love to publish favorable polls in hopes that they will convince fence walkers to jump on their "winning" bandwagon.
83.5% of all statistics are made up.