This is from a MSNBC news article:

Lyndon Johnson said the word “ni**er” a lot.

In Senate cloakrooms and staff meetings, Johnson was practically a connoisseur of the word. According to Johnson biographer Robert Caro, Johnson would calibrate his pronunciations by region, using “nigra” with some southern legislators and “negra” with others. Discussing civil rights legislation with men like Mississippi Democrat James Eastland, who committed most of his life to defending white supremacy, he’d simply call it “the ni**er bill.”