Does the 78 degree rule actually conserve electricity?

From my understanding, ACs cycle the inside air to make the inside air colder and colder till it reaches your desired temperature. So, if you set your AC at 68 degrees instead of 78 degrees, does it really use more electricity day to day, especially when it's already over 80 degrees outside day and night? Seems to me it really shouldn't after the very first hot day since the AC is only trying to maintain a 2-3 degrees range the whole time e.g. 67-69 when set to 68 or 77-79 when set at 78