Choose your facts

I picked up a copy of the Hartford Courant today and was reading an opinion piece by Jonah Goldberg.  Amidst a bunch of mysterious pop-culture references, a familar name jumped out:  James Stimson, a political science at UNC who has developed a measure of "policy mood":  basically, average public opinion on a liberal-conservative spectrum based on specific political issues, not self-description as liberal or conservative.  Then something surprising:  Goldberg said "In 2012, James Stimson, arguably America’s leading expert on U.S. public opinion, found that the country was more conservative than at any time since 1952."  I'm familiar with the policy mood measure, and that didn't fit with what I remembered.
   It turns out Goldberg is right:  see the policy mood data here.  He's also wrong:  see the policy mood data  here.  Here are the two measures shown on one graph (higher values mean more conservative).  They track each other closely until the early 1980s, and after that point have little in common

I don't know why. Neither of the data sites and none of the discussions and citations I've found mention the difference.