Trying to think of an issue that was 1) really important to Republican voters, 2) a Republican president made huge progress on it, and 3) those voters had no idea anything had happened. Can't come up with anything.
The better example is most GOP voters really have no idea what Reagan did with EO 12,291 and OMB review, which probably reshaped the federal regulatory field more than anything since the New Deal. Still impacting federal governance.