It's complicated, but if I were to sum it up, the answer would be: Pretty common. Predicting a percentage of anti-semitic lines of thought or the severeness thereof will be difficult - that's why polls like these are necessary - but there are few observations to make here.

Let's get into it. Let's first compare if there was a significant increase in anti-semitic influence in Germany during the Weimar Time.

This is a map of the German Empire's last big federal election of 1912. The brown-colored constituencies are the ones that have been won by parties that made antisemitism one of their leading political talking points, including the CSP, the DRP and the DSP. Sidenote: The DRP, when founded, initially called itself Antisemitische Volkspartei, anti-semitic peoples' party. So, just so you know, when I say "making antisemitism your main ideology", I mean it. These people were serious about the whole 'Jews are awful' thing.

But there is something interesting on that map - you see the local strongholds of the various political parties. Black correlates with catholicism, red correlates with generally industrialized areas, et cetera. Brown seems to be focussed in northern Hesse and has a few further outposts in Pomerania, Saxony and Lower Saxony. These areas have in common that they were rural, religiously protestant and not particularly wealthy.

And that's getting to the core of the question: Yes, antisemitism was widespread, very much so. Just like islamophobia is getting more and more of a phenomenon in the west in contemporary Europe and North America now that peripheral contact with islamic groups of people has increased. Having someone to point your finger at but having them be invisible enough to paint them as this malicious force is essential to xenophobic stereotyping. In 1912, you know the Jews are there, but you likely either never met one or if you did, you only were in brief contact with them. And then there was this angry politician dude who swore to God that the evil Jew next door is to blame for your problems. You might just go for it if you listen long enough.

Alright, so thats the position of the German Empire, before everything went down the gutter after the defeat in World War 1. SPD 35%, Z 16%, NLP 13%, FVP 12%, DKP 8%, Polish parties 4%, antisemites 2.5%, others up to 10%. Of the major parties, none held inherently antisemitic views, even though it could perhaps be argued that the more protestant-conservative forces were at least willing to tolerate them. So thats 2.5% antisemites, only 1 in 40! That's not bad, right? Well, maybe. 1 in 40 people in Germany hated Jews enough to give their political voice directly to a party that made antisemitism its main political talking point of choice. The other 39 in 40 still very much could have held similar views, even though perhaps not as severe. Analyzing these numbers heavily goes into speculation.

So let's look at Weimar itself. The first major election, in 1919, actually saw a massive resounding victory for the liberal democratic forces. The social democrats (SPD) got 38%, the catholic conservatives (Z) got 20, the market liberal DDP 18.5, the national conservative DNVP 10.3 and the radical leftist USPD 7.6, with about 6 going to all other parties. The SPD and USPD followed platforms of combatting anti-semitism, stressing Jewish participation in the Great War as a clear proof of Jewish patriotism and belonging to Germany and that the old protestant-Prussian elitist narrative of anti-semitism had been debunked. Many of the old guard of the Prussian/Imperial German apparatus had held anti-semitic views, up to Kaiser Wilhelm II himself.

Of these major political forces, only the DNVP represented a clear radical-conservative old order choice, so most antisemites would have probably gone for DNVP if their dislike of Jewish people was one of their main driving factors in political discourse.

So, from this assessment, it can be clearly said that inbetween 10% for DNVP in 1919 and 37% for NSDAP in July of 1932, a lot must have happened in the Weimar Republic. The NSDAP made anti-semitism one of their main political talking points, even raising the stakes by embracing and endorsing Hitler's Mein Kampf, which in 1925/26 had pretty clearly outlined the Führer's ideas regarding the belonging of the Jews to Germany as well as his foreign political ideas regarding the French and the Soviets.

Who voted for the Nazis exactly? The middle class as well as the urban working class. Most of the nazi voters were protestant, as catholics still generally preferred Z to NSDAP. So you see how this has shifted? From "rural low-income agricultural workers in northern Hesse" to "37% of Germany, carried by the middle class and urban workforce"? Hitler convinced these people to vote for him, and he did so by spreading anti-semitism.

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Sources and further reading:

• Childers, Thomas: The Nazi Voter: The Social Foundations of Fascism in Germany, 1919–1933. (1983)

• Hitler, Adolf: Mein Kampf. [two volumes] (1925, 1926)

• Kershaw, Ian: Hitler. (2008)

• Weitz, Eric D.: Weimar Germany: Promise and Tragedy (2007)

• Wucher, Albert: Marksteine der deutschen Zeitgeschichte 1914-1945. (1991)

• Zentner, Christian: Der Zweite Weltkrieg. (1981)