Whoever it is, I am pretty sure it is
not going to be Al Smith. The reason Smith was nominated with such little opposition in 1928 was that Democrats figured that Hoover was probably going to win anyway, so they might as well take a risk. Indeed, some 1924 McAdoo supporters thought that Smith should be nominated in 1928 precisely because they were sure he would lose--and thus discredit the northeastern "wet" wing of the party. "George Fort Milton described this sentiment to McAdoo in August 1927 as a desire to rid the party of the eastern 'menace' by 'nominating Smith and letting him have the terrific trouncing he is doomed to get.'" Douglas B. Craig,
After Wilson: The Struggle for the Democratic Party, p. 108. (This was pretty much the same line of thought which led Bryan to mute his criticisms of Alton B. Parker in 1904:
https://books.google.com/books?id=53zojBsecxcC&pg=PA157)
Indeed, even the northeastern conservatives like Raskob, who backed Smith as part of their stop-FDR strategy, did not expect Smith to be nominated. They were using him as a stalking horse for a more likely nominee (Newton Baker is often mentioned as their first choice.) In fact, it is doubtful that Smith himself thought he could win the nomination: "Smith's supporters ran a highly localized campaign, limiting their major efforts to Massachusetts, New York, New Jersey, Pennsylvania, Rhode Island, and Connecticut. Although Smith's name was entered in the California primary, for instance, he did not visit the state, and his campaign committee spent only $250 there." Craig, p. 232.