Hi there!
This question was sparked by a discussion with a friend. I claimed the Nazis were popular during WW2, while my friend claimed the opposite. I now realize I don't have anything substantive to back this claim, while my friend just has anecdotes. It certainly seems like an important question! (And a hard one to answer.)
I tried looking around for papers on this topic but couldn't find exactly what I was looking for. I am interested in the German public support for the Nazis post-enabling act, so the election results from 1932 aren't really what I am after.
My line of thinking is that the massive propaganda efforts, sense of nationalism and patriotism put forth by the Nazis, creation of a scapegoat (in the Jewish people), and a general "spirit" of the time associated with the Nazis would have contributed to popularity for the Nazis, but again I don't know if this is actually the case. And obviously, metrics you might use in a free and open society like "party membership" are probably basically useless in a totalitarian regime, so a clever way around this problem is needed.
The one thing I did find was this paper that claims anti-semitism among Germans educated during the Nazi reign is significantly higher than other age cohorts - suggesting Nazi propaganda can be effective. I would imagine there is a correlation between anti-semitism in Germany at the time and Nazi support, but this doesn't seem conclusive for my question either - since the youth don't represent the general population, and the correlation might not even hold.
Any insight would be very much appreciated!
This isn't quite the answer you're looking for, but you might be interested in this answer I wrote about polling of attitudes towards Hitler and Nazism in occupied Germany from 1945-1949.
Nazi Germany itself didn't conduct polls (which were a new thing anyway), nor did it have competitive elections, with the semi-exception of the March 1933 Reichstag election, which was after the Nazi seizure of power and the Reichstag fire (plus the Reichstag Fire Decree) but before the Enabling Act. It's worth noting there that despite the suspension of civil liberties and massive violence and intimidation at the polls, the NSDAP will only managed to gain about 44% of the vote, and only had a majority of seats in the Reichstag because of its coalition with the small far-right German National People's Party (DNVP). The supermajority needed to pass the Enabling Act relied on negotiations with the Catholic Centre Party (ZP or Zentrum), and only after that were other parties (including the DNVP) banned.
But anyway, to look at things from the other end, after the war, based on that linked answer. People's support was complicated and not exactly a binary thing. Support for Hitler (both qualified and unqualified) was different from support for the NSDAP as a party - Ian Kershaw has noted that Hitler as a leader actually had a much better image among Germans than the rest of the party. Support for the party also isn't the same thing as support for the goals or ideology of the party, even in areas of broad agreement (for instance, it was very much possible for those opposed to the Nazi regime at the same time to be anti-Semitic). And of course all of that doesn't account for people changing their minds over time. Those poll results after the war help parse those aspects out a little though.