It was Northern legislators from both political parties and President LBJ who pushed for it to get the Civil Rights Act of 1964 passed.
"In late November 1963 the assassination of John F. Kennedy changed the political situation. The new president, Lyndon Johnson, utilized his experience in legislative politics and the bully pulpit he wielded as president in support of the bill. In his first address to Congress on November 27, 1963, Johnson told the legislators, "No memorial oration or eulogy could more eloquently honor President Kennedy's memory than the earliest possible passage of the civil rights bill for which he fought so long."
Civil Rights Act of 1964 - Johnson and passage Wikipedia, the free encyclopedia
By party and region
Note: "Southern", as used in this section, refers to members of Congress from the eleven states that made up the Confederate States of America in the American Civil War. "Northern" refers to members from the other 39 states, regardless of the geographic location of those states.
The original House version:
Southern Democrats: 7–87 (7%–93%)
Southern Republicans: 0–10 (0%–100%)
Northern Democrats: 145-9 (94%–6%)
Northern Republicans: 138-24 (85%–15%)
The Senate version:
Southern Democrats: 1–20 (5%–95%)
Southern Republicans: 0–1 (0%–100%)
Northern Democrats: 45-1 (98%–2%)
Northern Republicans: 27-5 (84%–16%)