In many countries in Europe including largely Protestant ones such as the Netherlands and Germany, the Catholic parties were quite powerful in the prewar era and often held the balance of power. Was there any widespread Protestant support (ie as in voting for them) for Zentrum in Germany?
I can’t answer that question directly, but I think terming Germany a “largely Protestant country” with a Catholic party to balance is not entirely accurate. Denomination-wise, Germany is quite neatly divided: The Southern and Western parts are predominantly Catholic, the Northern and Eastern parts predominantly Protestant - at least that’s how it used to be, the East is now very heavily atheist/non-denominational, after 40 years of Socialism.
There are, and have been for centuries, Protestant enclaves in the predominantly Catholic South (e.g. Franconia in Catholic Bavaria), and also Catholic enclaves in the Protestant North (e.g. Paderborn). But these islands are well defined; there are areas that are predominantly one denomination, and then you cross an imaginary line and suddenly are in an area that’s dominated by the other.
This phenomenon is a remnant from the days when Germany was fragmented into literally hundreds of states or cities, each with its own government determining the official religion, at it was certainly even stronger pre-WWI than it is today. The overall numerical ratio might be slightly in favour of Protestants if you look at Germany as a whole, but Germany is not a predominantly Protestant country. That false impression might be due to the fact that Prussia, the most powerful German state, was officially Protestant - but when Prussia annexed the Rhine area around Cologne in 1815, which was and still is Catholic, Prussia was careful not to create the impression of suppressing the Catholic faith in that area.
From what I can see, in many countries, the ‘catholic’ parties seem to be just general moderate to conservative parties. They don’t seem to have many issues where their political positions are much different from those of conservative protestants. So I’d expect that a fair number of conservative protestants might find themself supporting the ‘catholic’ party at the polls.
Here in America, you often see the Catholic hierarchy working in lockstep with the Mormons and the most fundamentalist protestant sects on issues.
To clarify the OP’s misconception about Germany being a mostly Protestant country Schnitte pointed out, here’s the Wiki link to religion in Germany.
The same applies to the Netherlands, where Catholics account for 26.6 % and Protestants for only 16.8 % of the population.
Too late to edit: The link I provided states this:
So **Qin **still has a point.