The only democrat that has gone over 50% since 1964 is Jimmy Carter at 50.1%. No way Gallup can be believed.
The same could have been said about FDR. The only Democrat to get above 50% before FDR-1932 was Samuel Tilden and that was in 1876...56 years previous to 1932. But economic circumstances were a bit out of the ordinary in 1932. We have economic circumstances now that are a bit out of the ordinary as well.