This is the very first sentence from the document at the link you posted above.
Adults! Not registered voters or likely voters but just adults over 18 years of age. Can't help but wonder what the numbers might be for either of those groups.
It's not designed to be used to measure voters' opinions, but the opinions of those living in the US. There will be plenty of such polls out soon enough. Whether or not you believe it has any reliability, it's been in use for a lot of years, and a lot of presidents. Take a look at February 2009 and then the pattern over the past 5 1/2 years. The sample size, margin of error, weighting, and confidence level seem to be legitimate.
But if I'm voting in an election, I do want to see the surveys done with likely voters.