Harris won 55 percent of votes in his victory over Republican David Lenoir in Thursday's election for Shelby County mayor. Harris succeeds two-term Republican Mayor Mark Luttrell, who could not run again because of term limits.
Shelby County has about 930,000 people and includes the city of Memphis and its suburbs.
Harris is a University of Memphis law professor and a former Memphis City Council member. He served as the Senate Minority Leader in the General Assembly and has been outspoken on several issues, including his support of the removal of three statues of Confederate leaders from public parks in Memphis.
Lenoir played football at the University of Alabama and then worked in the financial services industry before he was elected to serve as the county Trustee - also known as the county's banker - in 2010.
The race had been contentious at times. Lenoir claimed Harris is weak on crime, and Harris said Lenoir has been part of a political establishment that lacks energy.
Experts said that a strong showing from Democrats in the majority-black Memphis could tilt the race toward Harris, who is African-American. Lenoir, who is white, was believed to have had strong support in the mostly-white suburbs.
Harris said he was surprised to see energetic supporters come to his campaign office and insist on paying for yard signs that usually are handed out for free. Harris said he campaigned in the suburbs as well as in "Democratic strongholds."
"We found that the message resonated, a message around investment in neighborhoods and investment in more opportunity for students," Harris told The Associated Press. "That worked all over."
Meanwhile, across the state in East Tennessee, voters in Knox County elected GOP candidate Glenn Jacobs as mayor. A small business owner and a WWE wrestler known as Kane, Jacobs defeated Democrat Linda Haney in the solidly-Republican county.
Knox County is Tennessee's third largest by population. It includes the city of Knoxville.
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