Vernon Bogdanor argued that:
----------------------
"Social democrat was originally a term applied to anyone from the Left  
who rejected the nineteeth-century liberal economy; it was applied to  
Karl Kautsky and H. M. Hyndman as well as to Eduard Bernstein and  
Anthony Crosland. Today, however, it forms but one element in the  
socialist spectrum, the revisionist element which began with the  
German social democrat, Eduard Bernstein, the hero of Berman's story.  
Revisionist social democracy was not, she believes, a mere "half-way  
house between Marxism and liberalism, cobbled together from elements  
of incompatible traditions"; nor were social democrats merely  
"socialists without the courage of their convictions"; nor should  
they be defined, as they were by Crosland, in terms of particular  
values such as equality. The essence of social democracy lies rather  
in "a distinctive belief in the primacy of politics", and an appeal  
to social and communal solidarity through mass political  
organizations – people's parties."

"These, however, are features that social democracy shares with its  
ideological enemies, Fascism and National Socialism. Social democracy  
and Fascism, so Berman believes, share a common genealogy, although,  
of course, social democracy is distinctive in being the only  
democratic movement of the three. The cover of The Primacy of  
Politics provocatively juxtaposes posters from the Swedish social  
democrats between the wars and the Nazis. Both promised work for all.  
For social democracy, like Fascism and National Socialism, arose out  
of the crisis of liberalism and Kautskyite Marxism at the end of the  
nineteenth century, philosophies which denied the primacy of politics  
and therefore seemed to countenance quietism, an approach which  
proved disastrous during the Depression. Thus, although, in both  
Germany and Italy, the socialists were the strongest political party  
after the First World War, they proved unable to defend democratic  
institutions."

"Moreover, social democracy found itself in retreat in the inter-war  
years everywhere in Europe except for Scandinavia, because it failed  
to appreciate the force of patriotism. The doctrine that the worker  
had no fatherland might, Bernstein conceded, have been true for the  
German worker of the 1840s "deprived of rights and excluded from  
public life", but by the beginning of the twentieth century, by which  
time he had voting rights and rights to social security, it had lost  
much of its truth; and it was given the coup de grâce in 1914 when  
the German SPD voted for war credits and the Second International  
disintegrated. "On August 2, 1914", declared Adrien Marquet, the  
French "neosocialist" who later identified himself with Fascism, "the  
notion of class collapsed before the concept of the Nation"."
----------------------


In the case of Germany, the Nazis were able to successfully implement
social democratic economic and social policies that the German business
community would have accepted, if an SPD-lead government had attempted
to implement.  And the reason for that IMO, is that the Nazis had also
taken care to smash the trade unions, thereby alleviating any fears on
the part of big business in Germany, that such policies would lead to
excessive (from their standpoint) wage hikes.  The Nazis were able to,
in effect, offer social democracy without Social Democrats.  And the
business community was willing to put up with this.