I have written about it before — the venom that South Carolina has historically injected into the nation’s political blood stream.

Let’s recount: South Carolina led the march to secession in 1860 and launched the country on four years of internecine slaughter. Since then, its politicians — men such as “Pitchfork Ben” Tillman, “Cotton Ed” Smith, and Strom Thurmond — have spewed their racial vitriol in the national forum. Throughout the 1990s, the battle over the Confederate flag atop the Statehouse mesmerized the nation and turned the state capitol into a rallying point for white supremacists.

Early in the 2000 presidential campaign, the Republican train moved from the Iowa caucuses to the New Hampshire primaries and into the Palmetto State. Along the way Sen. John McCain defeated Texas Gov. George W. Bush in Iowa and routed him in New Hampshire. One more defeat and Bush would have been on his way back to Austin.

But in South Carolina, a mysterious — and now legendary — smear campaign of last-minute phone calls and fliers made sure that wouldn’t happen. Potential voters were told, among other things, that McCain’s wife was a prescription drug addict and that the senator was the father of an illegitimate black girl. Both charges were untrue — and the second, too ironic to have happened anywhere except South Carolina. But enough voters believed it. More importantly, they were sufficiently outraged to go forth and give the primary to Bush and launch him on his way to the White House. It can be argued that all the corruption, malfeasance, diplomatic wreckage, and fiscal mismanagement wrought by this administration can be laid at the feet of the Palmetto State.

Now our perverted values have once again poisoned the well of national politics.

Coming into the Democratic primary last week, Barack Obama was heralded as a new kind of politician. His caucus victory in overwhelmingly white Iowa seemed to prove that he transcended racial politics. By uniting blacks and whites, he would show the way to a new post-racial America.

Then he hit the Palmetto Jungle, where nothing is without racial tint.

Politics being what they are in this state, the vast majority of white people vote in the Republican primary and an even larger majority of blacks vote in the Democratic primary. (Approximately 55 percent of Democratic voters on Jan. 26 were black.)

In the months leading up to that primary, polls showed Obama and Hillary Clinton running neck-and-neck to capture the state’s black vote. Indeed, a number of the state’s black political leaders — including Sen. Robert Ford of Charleston — had endorsed Clinton.

And why not? Bill and Hillary Clinton are long-time civil rights champions. The empathy between black folk and the poor white boy from Arkansas is legendary. Poet Maya Angelou boldly declared Bill Clinton to be “America’s first black president.”

Whether Bill Clinton was a loose cannon or was taking orders from his wife’s campaign in the week before the primary is still not clear. What is clear is that somebody felt that desperate measures were called for in this critical state.

Bill Clinton uncorked the racial rhetoric, saying that he feared his wife could not win in S.C. because Democrats would be voting on racial identity. On another occasion he compared Obama to black activist Jesse Jackson, who ran for president in 1984 and 1988. In those years Jackson made good showings in the S.C. Democratic primary, but did not come close to winning the nomination. It was a thinly veiled reminder that a black candidate was unelectable.

By most accounts, Clinton’s rhetoric backfired. Obama defeated Hillary Clinton 55 percent to 27 percent. But exit polls show that while he carried nearly 80 percent of the black vote, he got only 25 percent of the white vote.

The damage that was done in South Carolina was extensive. Barack Obama was “racialized.” He came out of the state looking like the official “black candidate.” Will he be able to shake that image down the stretch to the August convention? He is still a long shot to win the nomination, but the odds of victory are even slimmer in the general election if he is branded the “black candidate.”

And what about Bill Clinton and his legacy as a racial moderate? That legacy took a serious hit in South Carolina, as did his reputation as a brilliantly instinctive politician. Not only did he alienate black voters and cause his wife to lose by a landslide, but he left the state with a new reputation — the man who played the race card. I’m betting his wife’s campaign will recover from this disaster before his image does.

Such is the power of South Carolina to racialize politics and bring out the worst in good people. It’s a curse we bear and we impart to the nation and we seem unable to exorcise it.