Disfranchisement and the Solid South
Main article: Solid South
After the American Civil War, Southern states gained additional seats in the House of Representatives and representation in the Electoral College because freedmen were granted full citizenship. They were also granted suffrage. Southern white resentment stemming from the Civil War and the Republican Party’s policy of Reconstruction kept most southern whites in the Democratic Party, but the Republicans could compete in the South with a coalition of freedmen, Unionists and highland whites.
Rising intimidation and violence by white paramilitary groups such as the White League and Red Shirts during the mid to late-1870s contributed to turning out Republican officeholders and suppressing the black vote. After the North agreed to withdraw federal troops under the Compromise of 1877, white Democrats used a variety of tactics to reduce voting by African Americans and poor whites. In the 1880s they began to pass legislation making election processes more complicated.
From 1890 to 1908, the white Democratic legislatures in every Southern state enacted new constitutions or amendments with provisions to disfranchise most blacks and many poor whites. Provisions required complicated processes for poll taxes, residency, literacy tests and other requirements which were subjectively applied against blacks and poor whites. As blacks lost their vote, the Republican Party lost its ability to effectively compete.<5> The feature "Turnout for Presidential and Midterm Elections" at the University of Texas Politics: Historical Barriers to Voting article shows the dramatic drop in voter turnout as these measures took effect, and also their longevity in Texas and across the South. It also shows the comparison of Texas and southern voting compared to the rest of the US.<2>
The South became solidly white Democratic until past the middle of the 20th century. Effectively, Southern white Democrats controlled all the votes of the expanded population by which Congressional apportionment was figured. Many of their representatives achieved powerful positions of seniority in Congress, giving them control of chairmanships of Congressional committees. African Americans could not elect one person to represent their interests and filled no local elected offices, where government was closest to the people. Because they could not be voters, they were also prevented from being jurors and serving in local offices. Services and institutions for them in the segregated South were chronically underfunded.
http://en.wikipedia.org/wiki/Solid_South