At least twice in this thread I have posted - and agreed with - the 1984 (64%) number.
Gallup actually has 1972 at 68%.
Very easy to calculate if the 67% and 68% numbers are accurate - and they are not.
In 1972, 90%-91% of the voters were white.
In 1972, Nixon's certified vote total was 60.7%.
Gallup claims that only 13% of non-whites voted for Nixon, which would be the lowest number in modern history.
Multiple sources challenge that and claim that Nixon received about 18% of the Black vote and about 35% of the Hispanic vote.
If you plug in Gallup and NYT exit numbers, you do not get Nixon at 60.7%. You get Nixon at about 63%-64%.
Around 1980, exit poll takers started “norming” their numbers. In other words, they adjust their exit polls until they agree with the actual results.
If you want to claim that Nixon got 64%, that's possible, and I won't challenge you.
If you claim 67% or 68% like NYT and Gallup, the certified election results do not support that math.
I’ll go with the exit polling data, not your system.