A special election will be held to replace Emerson, who was first elected to the House in 1996 to replace her husband Bill Emerson, who died in office that year. She represents Missouri's 8th District, which lies in the southeastern part of the Show-Me State.
The congresswoman was easily re-elected in November with nearly 72 percent of the vote in a heavily Republican district. During her tenure in the House, Emerson crafted a moderate profile. According to National Journal's 2011 vote ratings, she ranked near the middle of the pack, clocking in as the 200th most conservative member of the lower chamber.
Given the GOP-tilt of the district, Republicans will be heavy favored to hold the seat. Republicans familiar with Show-Me State politics pointed to several possible GOP candidates for Emerson's seat including state Rep. Jason Smith, former state representative Mark Richardson, former treasurer and 2012 Senate candidate Sarah Steelman, state Republican Party Executive Director Lloyd Smith (who is Emerson’s former Chief of Staff), Lt. Gov. Peter Kinder, and incoming state Sen. Wayne Wallingford.
The 8th District Democratic and Republican Party Committees will choose nominees; no special primaries will be held.
Emerson sits on the House Appropriations Committee, chairing the Financial Services and General Government Subcommittee. In her statement, she said serving her district has been an honor and a challenge.
"The people of Southern Missouri have entrusted their voice in Congress to me for 16 years. Serving them is a humbling experience, a great honor and a welcome challenge. Our congressional district is big, it is diverse, and it demands practical representation by someone who places us and our home ahead of politics and partisanship. The people of our district demand results, they want us to work together, and they have every right to a representative who works as hard as they do. Every day in Congress, that is my goal," Emerson said.
House Democrats' campaign arm reacted to Emerson's announcement by arguing that the GOP conference has grown too conservative for moderates Republicans.
“Congresswoman Emerson is the latest moderate Republican to ditch House Republicans, a sign that no moderates are welcome in the Tea Party House Republican Caucus," said Democratic Congressional Campaign Committee spokesman Jesse Ferguson.
Incoming National Republican Congressional Committee Chairman Greg Walden (R-Ore.) praised Emerson and wished her well for the future.
"As the first Republican woman to represent Missouri in Congress, Jo Ann Emerson has been a principled, determined voice for Missouri families and small business owners. During her 15 years in Congress, Jo Ann has focused on protecting farm families, promoting American agriculture, and working to create jobs," Walden said.
Emerson's announcement comes nearly two weeks after Democrat Jesse Jackson Jr. announced his resignation in Illinois's 2nd District. The special election to replace Jackson will be held next April.