What this thread ignored was the impact of generational demographics.
Since birthrates among the immigrant Catholics was higher and also because those children would be naturalized citizens and voters, the Lost and then even more so, the Greatest Generation, were far more ethnically diverse with the city white populations becoming overwhelmingly ethnic white and Catholic. This meant that you would have such massive and large gains in votes from one election to the next and this was evident in 1928 as Smith being a Catholic, meant that he could tap into that vote in a big way for the first time. But nothing compared to the motivational force of the Depression to turn out and vote, and the number of voters ballooned over the next several years.
That is why if I am not mistaken, polling had Landon ahead in MA. When it came to the weath skew in those polls, that meant that an older, Protestant demographic was over represented and one that was far and away out voted on the ground.
Obviously it's not apples to apples, but I vaguely remember reading one time that there were actually a few publications making similar predictions as today at that time: that demographics were eventually going to catch up with the heavily Anglo, heavily Protestant GOP and that they'd eventually need to reach out to ethnic Whites and Catholics, haha. Kind of funny to look back on considering the current narrative on demographics.
Yes and eventually Republicans decided to give up liberalizing to chase a moving target in NY and MA and instead pursued a sunbelt, "Southern Strategy".
Of course the Republicans adapted on some key issues to mirror more closely the sunbelt on policies like immigration, trade and foreign policy.