Even Nelson Rockefeller's biggest legacy is the Rockefeller Drug Laws. This myth probably also comes from some fairly recent Republican Presidents who for the most party governed pretty unideologically and not exactly conservative or liberal (Eisenhower and Nixon) and the fact that the Republicans of the time were mostly not fire breathing zealots like today, but there's no point in the 20th century when you can put the Republican Party to the left of the Democratic Party in general and when progressive Republicans were anything but a small insignificant faction.
As far as I'm concerned, Nelson Rockefeller's biggest legacy (and it is a tremendously positive, progressive one) is dislodging the Dark Lord Robert Moses from his Satanic throne underneath the Triborough Bridge... but I admit I'm weird.
And there is
one point in the 20th Century where you can put the Republicans to the left of the Democrats, and progressive Republicans were a major faction. That point is the election of 1904.
I agree with the rest of this though. Just some minor nitpicks.