The Council of Conservative Citizens opposes “all efforts to mix the races,” and believes “that the American people and government should remain European in their composition and character.” It would severely restrict immigration, abolish affirmative action and dismantle the “imperial judiciary” that produced, among other rulings, the 1954 Supreme Court decision that integrated American education.

Those are among the core principles of the council, a Missouri-based organization with a long history of promoting white primacy. Now the massacre of nine black parishioners in a Charleston, S.C., church has propelled the organization, which in recent years seemed in decline, back onto the national stage and embroiled the Republican Party in new questions about its ties to the group.

Many of the themes promoted on the council’s website resonate through an online manifesto apparently written by Dylann Roof, who has been charged in the killings last week in Charleston. The manifesto traced the motivation for the shootings to a twisted epiphany: a Google search that led to the council’s website, where “pages upon pages of brutal black on White murders” were tallied and described.

“I have never been the same since that day,” the manifesto attributed to Mr. Roof said.

Since it rose in the 1980s from the ashes of the old and unabashedly racist White Citizens’ Councils, the Council of Conservative Citizens has drifted in and out of notoriety. But it is clearly back in: Last weekend, three Republican presidential candidates — Senator Ted Cruz of Texas, former Senator Rick Santorum of Pennsylvania and Senator Rand Paul of Kentucky — announced that they were returning or giving away donations from the council’s president, Earl Holt III.