Most of us here on DU are very high information types, even though there's a wide range of opinions on all topics. We care a lot, we pay attention to what's going on, and we post here. We also vote.
The other thing is that almost everyone owns a TV and watches several hours a day, so all political season they see political ad after political ad after political ad. And decide how to vote based on that.
Or, they've been -- their family has been -- Republican since the Civil War and they honestly don't get how much things have changed.
Or they watch Fox News, nothing but Fox News, and have not a clue how much of what they see there is completely untrue.
Or they're sincere Christians who do really believe the Gay has plans to destroy their marriage.
And on and on.
Even good public schools don't really teach critical thinking to kids, and so most people have no way of assessing what they hear or see. I forget what the exact numbers are supposed to be, but probably about half of all adults never read another book after they leave high school. Of those who read books, I think it's around half who read about one book a year. The rest of us read much more than that, but we're still in the minority.
So it comes down to the simple fact that most voters are unaware of the real issues, but vote on them and for candidates nonetheless.