that I've found for my black ancestors c. 1900 and before showed they were Republicans. One of them was killed in 1876 for being a "radical Republican" who was urging the community to vote. He was described as "a strong, influential and tolerant partisan of the Republican party, and was especially obnoxious to resident Democrats on the Island."
http://files.usgwarchives.org/la/state/newspapers/afriamer/ouachita2.txt This may give you and idea.
An excerpt:
The Ouachita Telegraph
Friday, December 1, 1876
Page 2, Column 5
GOOD REPUBLICAN EVIDENCE
We give below a sample of the Radical testimony presented before the
Returning Board relative to the late canvass. Both of the witnesses are
negroes, but swear with the endorsement of their white leaders. The report
is copied from the New Orleans Democrat, that in the Republican is tenfold
more virulent:
Wells announced that the Ouachita case would be taken up. The
Democratic Committee protested on the ground that it had been agreed that East Baton
Rouge should be the first contested parish considered. Wells declared the
ruling of the board changed. The witnesses were ordered to be brought in.
Frank Morey, of the Republican State Committee, said that it was the
intention of the Republican counsel to prove intimidation by the Democrats;
that negroes were threatened with death if they did not vote the Democratic
ticket; that the white Republican leaders were murdered; that the citizens
massed at the different boxes, and that the negroes were intimidated into
voting Democratic.