There's a spirited debate going on here over the historic racist legacy of the Democratic Party, and the more recent dominance by the GOP in the South. The Bartlett position, as I understand it, is that the Democratic Party for many years relied on the support of avowed racists in building its electoral dominance after 1930, and was for many years before that the partisan bulwark of white supremacy in the South. Such views were not the sole province of Southern rednecks, either; non-Southerners, like FDR, Woodrow Wilson, William Jennings Bryan, and the editorial board of the New York Times, circa 1900, expressed views about the participation of non-whites in our political system that would, under any definition, be considered vile.
Of course, such positions were also shared by Republican officeholders of that same period. White politicians were a lot more racist back then, largely because white voters in both the North and South were a lot more racist, and it wasn't unusual for a political figure to try to court both blacks and bigots in the same election, or to zig-zag between different forms of populism, one of which embraced interracial harmony against the plutocrats who sought to divide the oppressed masses by skin color, versus another which relied on racial and ethnic stereotypes that would find their fullest expression in Central Europe in the 1930's and '40's.
It would not be hard to cherry-pick from the collected quotations of such luminaries as Abe Lincoln, Teddy Roosevelt, William McKinley and Calvin Coolidge to find instances where such politicians might have trouble winning votes in Harlem or Oakland today. The complete disenfranchisement of African Americans in the South, as well as the entrenchment of Jim Crow policies, occurred between 1876 and 1932, a period in which the Republican Party controlled the federal government for all but sixteen years. As far back as the Election of 1900, Democratic candidates for President were covertly seeking the votes of Northern African-Americans who had felt spurned by the Republican Party, and W.E.B. DuBois even went so far as to endorse Bryan in the 1908 Election. By the time of the Great Depression, it was inevitable that the party with the strongest political base in the Northern cities was also going to capture the votes of African Americans, and that proved to be the critical reason for the sudden partisan shift in how the descendents of the people freed by the Party of Lincoln became Democrats.
But just as it's false to suggest that the Democrats were the only racist political party in America for much of its history, so to is it false to claim, as Paul Krugman and Matthew Yglesias do, that the post-1968 dominance by the GOP at the national level was caused by its pursuit of a "Southern Strategy" followed by Richard Nixon and Ronald Reagan. One can actually see a decided shift in partisan allegiances dating back to the 1928 election, when Herbert Hoover captured several states in the Deep South against Al Smith. Southern states like Texas, Florida, Virginia, Oklahoma, Kentucky, and Tennessee were swing states thereafter, and even segregationist Louisiana voted for Dwight Eisenhower in 1956, two years after the President's nominee for Chief Justice of the Supreme Court, Earl Warren, had helped overturn segregation in public schools.
In fact, Republican hegemony in the South is a much more recent trend, effectively dating back to the 1994 mid-term landslide. Whatever nefarious machinations may have been intended by Kevin Phillips and Lee Atwater, the net result was not immediately apparent. In 1960, JFK squeeked by Richard Nixon in a race that saw the losing Republican candidate win Florida, Virginia, Oklahoma, Kentucky and Tennessee. Eight years later, Nixon won eighty-two more electoral votes and the election, but only added the Carolinas to his Dixie tally; infinitely more important to his success was winning over former Democratic voters in Illinois, New Jersey and Missouri, states without which Kennedy could not possibly have won in 1960. When it was all said and done, the South was largely a sideshow in that election, as it would be in each Republican victory through 1988.
Even in 1980, the year Reagan famously used the code words "states rights" in the city where Goodman, Cheney and Schwerner had been lynched, the South ended up being Jimmy Carter's most competitive region. Ironically, it has been the reemergence of a new "Solid South" backing the GOP since 1992 that has proved to be most detrimental to the party at the national level. After easily winning four out of five Presidential elections from 1972 to 1988 with a national coalition, Republicans have now lost the popular vote in three of the last four, and have seen their regional bases dwindle to the South and the sparsely populated states of the Rocky Mountains and Great Plains. As the 2006 mid-terms show, that's a recipe for long-term political exile. It may be convenient to lay past disappointment for liberals and progressives at the feet of a malevolent racist conspiracy, but the truth is far more complicated.