How did the Republican party become racist?

From dKosopedia

Through the course of American history, the allegiance of the African-American vote has swung between the two major parties, often dictated by events.

It was naturally aligned with the Republican Party, the party of Abraham Lincoln, in the post-Civil War era. That allegiance, however, began to shift during the early decades of the 20th century.

Many African-Americans migrated to the northern industrial cities and northern Democrats, with their eyes on electoral gains, began to woo their vote. At the same time, Republicans, facing electoral losses after being branded the party of African-American voters, began to retreat on their promises and intentionally try to get the vote of racist white southerners.

Two pivotal events followed: President Harry Truman, a Democrat, integrated the armed forces in 1948 and another Democratic president, Lyndon Johnson, aided by a number of liberal Republican lawmakers (and all non southern Democrat Lawmakers), enacted the Civil Rights Act in 1964.

Meanwhile, many white southern Democrats, who did not embrace the politics of their northern brethren, began a steady migration to the Republican Party following the presidential election of 1964, further cementing the allegiance of African-American voters to the Democratic Party.

Since the 1964 presidential election, the Democratic Party has won overwhelming majorities of the African-American vote, Fauntroy said.

In 2008 the Democratic Party has a considerable edge when measuring party identification among African-American voters, according to a Pew study released in March, 2008. Of those surveyed, 72 percent identified themselves as Democratic. In contrast, 4 percent identified themselves as Republican.

In 2004, African-American voters encompassed 11 percent of the electorate, according to a U.S. Census Bureau study published in March, 2006, and new voter registration statistics suggest those numbers may rise in 2008 with the election of Barak Obama.[1]