I've often tried in vain, but now I might have found the source(s): click for a scholarly website about this citation

First, they came for the Jews is historically wrong and Niemöller never would have said that. Correct is: first they came for the communists though this line is omitted in several English language versions. Even some holocaust memorials get it wrong.

Each one seems to misquote according to his or her own agenda. Gore, for instance, never cites the line about the trade unionists but loves to include the Roman Catholics that never have been mentioned by Niemöller in this context.

As late as 1979, in Blätter für Deutsche und Internationale Politik (not cited in Marcuse's website as far as I see), Niemöller did write first communists, then social democrats, then him.

He was arrested in 1937 a year before the large scale arrests (and murders) of the Jews and after the arrests of communists and Social democrats. So his time-line makes personal sense.

However, I know that this citation now has a life of its own and most people do not care about correctness.

Wolfgang