Overall, Smith earned 45,301 votes compared to Harrell's 41,149.
"I'm real pleased to win," Smith said. "I'm looking forward to taking the job. I really appreciate the people who supported me and who trust me to get us through this bad economy."
He said he was not surprised the race was tight between he and Harrell.
"I thought it would be very close," Smith said.
He said he appreciates the clean race between the two of them, and he hopes to maintain the friendship they developed on the campaign trail.
District 1 commission seat was earned by Republican candidate Bo Moss, who beat Democratic candidate James C. Mays by 2,918 votes out of a total 15,760. Moss secured an overwhelming percentage of the vote at 59.17 to Mays' 40.68 percent.
Incumbent Brian Preston won his bid for re-election to District 2, narrowly edging out Democratic candidate Jackie Anderson-Woods by 1,424 votes. Preston earned 53.9 percent of the vote to Woods' 46.04 in the second district.
For the presidential election, Henry County voters selected Mitt Romney over Barack Obama by slightly more than a percent margin.
Romney earned 51.07 percent of the vote against Obama's 47.85 percent. Romney's 46,271 just edged out Obama's 43,360 with a difference of 2,911 votes.
A total of 90,438 voters came out to the polls, out of the county's 123,177 registered voters.
The turn out percentage was 73.42, which Election Director Janet Shellnutt said she was roughly 75 percent.