The Eye

That is because Cohen, who is white, has represented Tennessee's only black-majority district since winning the 2006 contest for the seat that Harold E. Ford Jr., an African-American Democrat, had left open for a U.S. Senate bid that he narrowly lost to Republican Bob Corker.

Although Cohen is a liberal Democrat who cultivated support from black voters during a long tenure in the state Senate, there are a number of black activists who remain dissatisfied that the 9th District does not have African-American representation. These critics contend that Cohen won the 15-candidate primary in 2006 with 31 percent of the vote because he was the only strong white candidate in a field that included several competitive black candidates.

That proposition was tested in 2008 by Nikki Tinker, a lawyer who finished second to Cohen by 6 points in that 2006 primary, but Cohen easily won that Democratic matchup after the challenger ran a controversial campaign that included ads that sought to associate Cohen, who is Jewish, with the Ku Klux Klan.

Herenton, however, shapes up as a much more formidable opponent for the 60-year-old Cohen.

Herenton, who will turn 70 years old next spring, formed an exploratory House campaign committee in April. In explaining his decision to resign as mayor, Herenton said Thursday that holding one office while pursuing another would create a conflict of interest.