The Radical Republicans were the leading political force during the time of Lincoln through the Reconstruction period. With strong belief in the 1783 Constitutional language that all men are created equal [reverece toward the Jefferson-Madison ideals], they campaigned to enhance freedom through free market economics. During this time, the northern states were majority Republican and had established a vibrant free market society. The majority Democrats in the south maintained a European model of an upper class minority supported by cheap labor of black slavery and poor whites.
In 1862 the Radical Republicans literally went to war against slavery with support of the moderate President Lincoln. After the Civil War and slavery was finally abolished, the southern Democrats kept the lower classes in line by limiting civil rights. The strong Republican majority in congress overrode a veto from Democrat President Andrew Johnson for the first time in US history and passed the Civil Rights Act of 1868. The racist Johnson then refused to enforce it.
Republicans passed the Civil Rights act of 1875, which was struck down by the Democrat majority Supreme Court in 1883. Republicans tried again in 1957, watering down a Civil Rights Act to overcome stiff Democrat opposition. 1960 brought a third Republican Civil Rights Act, pushed through after nearly a week long Democrat filibuster.
President John Kennedy became the first Democratic President to embrace the conservative ideals of the Radical Republicans. Democratic President Lyndon Johnson, who himself grew up impoverished in the South, pushed his party further, and supported the Republican sponsored 1964 Civil Rights Act. This Act was essentially a re-writing of the 1875 legislation, and was passed against chief opponents Albert Gore Sr. and a 14 hour filibuster by former Klansman Robert Byrd, still a Democrat senator to this day. Johnson was instrumental in strengthening the Act in 1968.