The German population before WW2 was roughly half Catholic half Protestant. Before and during WW2, was there any significant disparity between the support for NSDAP across the religious line? In other words, was one of the religious groups more Nazi than the other or was it pretty even?
This article shows maps of the German census and election results of 1932, showing what appears to be a clear link between Protestanism and Nazism.
BUT, this only reflects the 1932 elections. These were held during a time when the Vatican forbade Catholics from support fascism and naziism.
By the time of the November 1933 elections that put the NDSAP in power and Hitler as Reichskanzler, this had been changed and the Vatican now condoned fascism and naziism. As a result the 1933 election results show near universal support for the NDSAP across religious lines (when taken by general area) though still less in the border regions with France, the Czech Republic, and Austria).
My guess is that many Catholics didn't vote NSDAP in 1932 because of the strictures placed on the party by the Church, and once those strictures were lifted voted what they wanted, NSDAP.
The German population before WW2 was roughly half Catholic half Protestant.
That's not strictly true. According to Population by Religious Denomination (1910-1939) from the GHDI, 62.7% of 1933's population identified as protestant, while 32.5% identified as catholic; the Protestants outnumbered the Catholics almost 2:1.
Before and during WW2, was there any significant disparity between the support for NSDAP across the religious line?
Support for the conservative and politically Catholic Z/BVP—the Catholic Centre Party— was practically constant in the last five free general elections (December 1924, 1928, 1930, July 1932, and November 1932), changing from 15.1%, to 14.8%, to 15.7%, to 15.0%. They also remained largest party in predominantly Catholic constituencies, implying that a large portion of the Catholic minority voted for Z/BVP.
Meanwhile, support for non-Z/BVP conservative parties and non-NSDAP right-wing parties diminished severely. In December 1924, the nationalist-conservative DNVP, the right-wing liberal DVP, the far-right NSFB, the conservative WP, and right-wing LB together occupied 38.2% of the seats in the Reichstag. In July 1932, the aforementioned parties and three other minor ones (CSVD, DL, VRP) held only 8.7% of the seats, while the NSDAP managed to seize 37.8% of them.
In other words, was one of the religious groups more Nazi than the other or was it pretty even?
It's much harder to answer that question. It also depends on what definition of Nazism you're using.
If you simply mean voting for the NSDAP, that seems to be the case. Center-to-right Catholics didn't switch to the NSDAP nearly as much as center-to-right Protestants did. Left-wing voters mostly kept voting for left-wing parties anyway...
If you mean the historical definition of Nazism (the political principles of the NSDAP), I'm not so sure anymore. Note that one of these political principles was anti-Communism, which caused even Pope Pius XI to express support for the Nazis by saying
I have changed my mind about Hitler, it is for the first time that such a government voice has been raised to denounce bolshevism in such categorical terms, joining with the voice of the pope.
More or less at the same time, the Catholic Centre Party unanimously voted in favor of the Enabling Act, through which Hitler seized absolute power in March of 1933. Of course, all of this support was based on false promises to leave the Catholics and the Centre Party alone...
If we go by the modern definition of Nazism (based on what they actually did, not just their political principles), I'm not so convinced that that many people were Nazis in the first place.
The Great Depression, the record unemployment rate in 1933, and the repercussions of The Great War made people susceptible to the propaganda of the National Socialist German Workers' Party; they hoped Hitler would save them and—at least at first—they didn't care what they would have to give up in return or how it affected other people. In the last free election (November 1932), after the NSDAP had been the dominant party for only three months, they went from 37.3% of the popular vote to 33.1%, so it seems many people had already realized that they made a mistake...