According to a recent study by the CSV institute, older Americans are prone to adopting right-wing ideologies due to exposure to tetra-ethyl lead fumes during their formative years. Right wing ideology has been clearly associated with a lack of intelligence and a tendency towards inter-group paranoia. Lead makes people stupid and paranoid. Ergo, as we raise generations that have had less exposure to lead paint and tetraethyl lead gasoline fumes, we'll see people become more intelligent on average. As individuals become more intelligent, they are less likely to become conservatives.
To paraphrase the classic phrase: "If you're a conservative at 20 then you probably have an autism spectrum disorder. If you're a conservative at 60 then it's probably because you were exposed to a lead of lead paint and gas fumes when you were a kid."