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The appointment of Rep. Tim Scott of South Carolina to the Senate and the likely candidacy of Newark Mayor Cory Booker creates the possibility of a surprising new dynamic: two black members of the U.S. Senate.

Only six blacks have ever held Senate seats, and none of them served together. This would be far from a representative group of African-Americans in the chamber, as blacks are about 13 percent of the U.S. population.

But it would also be a sign of progress, as the Senate has largely had zero or one black member for much of its history.

To be sure, nothing is guaranteed, as both men would have to win elections in 2014. Scott is now a heavy favorite, an incumbent in a Republican state where he is unlikely to face a primary challenge and is virtually guaranteed to win in a general election. But Booker must hope the 88-year-old Democrat currently holding the Senate seat, Frank Lautenberg, either steps aside or is easy to defeat in a primary.