Even if the Republicans managed to distance themselves from the thinly veiled racism of the Tea Party adherents who have moved the party rightward, they wouldn’t do much better among black voters than they do now. I suspect that appointments like Mr. Scott’s are directed less at blacks — whom they know they aren’t going to win in any significant numbers — than at whites who are inclined to vote Republican but don’t want to have to think of themselves, or be thought of by others, as racist.

Just as white Southern Democrats once used cynical manipulations — poll taxes, grandfather clauses, literacy tests — to get around the 15th Amendment, so modern-day Republicans have deployed blacks to undermine black interests, as when President Ronald Reagan named Samuel R. Pierce Jr. to weaken the Department of Housing and Urban Development, Clarence M. Pendleton to enfeeble the Commission on Civil Rights and Clarence Thomas to enervate the Equal Employment Opportunity Commission.

Over the course of history, racial alignments have shifted radically. The Democrats were the party of white supremacy until the New Deal. The Republicans were a party of relative, if feeble, support for civil rights until the 1950s. The tables have completely turned. No Republican presidential nominee has won the black vote since 1936. All four black Republicans who have served in the House since the Reagan era — Gary A. Franks in Connecticut, J. C. Watts Jr. in Oklahoma, Allen B. West in Florida and Mr. Scott — were elected from majority-white districts.

There is little that connects these men to mainstream black politics or to the country’s first two black senators, Hiram R. Revels and Blanche K. Bruce, who were elected (by the Mississippi State Senate) during Reconstruction, that extraordinary and brief moment of African-American political empowerment after the Civil War destroyed chattel slavery.

Not until the Great Migration of blacks to Northern cities between the two world wars were they again capable of electing candidates of their choosing. In the South, blacks began to register to vote in substantial numbers only after the Supreme Court overturned the “white primary,” which had allowed Southern Democrats to exclude blacks by defining the party as a private club, in 1944. The Voting Rights Act in 1965 turned the trickle of black politicians into a flood.