Shh... don't tell anyone!
Seriously, the migration of black voters from the Republican to the Democratic party is as profound a switch as that of the South from Democratic to Republican. I haven't heard a really good explanation of why black voters switched (that doesn't involve screaming "racists" as this columnist does). Martin Luther King's father was a Republican, for instance. One history book I read said it was mostly the result of FDR, and that since black Americans were hit harder by the Depression than others, the loyalty to FDR and his party was stronger.
So this is part of it, but what else? Sure there are racist Republicans, but there are racist Democrats too. Is the Republican position on affirmative action solely responsible for the lopsided results now?
It did indeed start with Roosevelt. But blacks did not vote lockstep Democrat in the massive numbers seen today until the passage of the Civil Rights Act and Voting Rights Act in the mid-1960's. LBJ, a Democrat, made sure that word got out that black voters could only trust Democrats.
It was a remarkable piece of rhetorical slight of hand, since the Southern Democrats such as George Wallace were among the most virulent racists in the country at the time. (Wallace later repented of his racism.)
Today, the Democratic Party has a social, political, and psychological hold on the black community beyond anything the Republicans have even among there staunchest supporters. Many blacks really do think that the Republican Party is systemically racist and would wipe them out if they could, and that the Democrats are the only ones that stop that from happening. It sounds ridiculous to us, but that is why Gore could get away with hinting in a black church that Bush is in favor of slavery. Many of the folks in the congregation probably believed it.
The feelings by blacks against Republicans are so strong that Republicans will not break into the black community for at least a generation. That is too bad - I think that blacks would find a lot to like about the Republican Party.
Here is an interesting statistic. Zogby did a poll a few years ago and discovered that blacks support the agenda of the religious right - pro-life, pro-family, etc., more than any other ethnic group. It is clear that blacks are very church-going, God-fearing, conservative folks. Yet they vote for the most anti-family candidates imaginable, every single time. It really is a fascinating case study in political science, in addition to being very regrettable.