Why aren't there any black Senators?

James Taranto reacts to the inflammatory assertion that "Mark Kirk Re-Segregates the Senate." It's true that "of the four blacks who've served in the U.S. Senate since Reconstruction, three of them held what is now Kirk's seat: Carol Moseley Braun, Obama and [Roland] Burris." So a black person's chances of getting elected to the Senate seem best in Illinois, but it didn't happen this year. But why aren't black candidates more successful in running for statewide office? Taranto blames the Voting Rights Act:

In the interest of increasing minority representation in the House and state legislatures, the act mandates the drawing of "majority minority" districts.

On its own terms, this has worked very well. The size of the Congressional Black Caucus relative to the House is within a few percentage points of the black proportion of the population. Seats in state legislatures and the House frequently are stepping stones to statewide office. But because black politicians need not cultivate a transracial appeal to win office in the first place, they are at a disadvantage when they consider a statewide run.

Moseley Braun and Obama are exceptions. (The unelected Burris is irrelevant to this analysis.) Before being elected to the U.S. Senate, both served in the Illinois Legislature from Chicago's Hyde Park, which, although a decidedly left-wing constituency, is one of the most racially integrated in the nation.