Colleagues and congressional analysts expressed surprise and dismay Monday after learning that U.S. Rep. Jo Ann Emerson of Missouri had decided to quit.
Within minutes, though, the state's politicians began pondering the race to replace her.
Emerson, a 62-year-old Republican from Cape Girardeau, announced her retirement less than a month after southeast Missouri voters overwhelmingly elected her for the ninth time. She will become president and CEO of the National Rural Electric Cooperative Association in March.
"Our district has earned its reputation for common sense above all else, and I will leave Congress in February with a heavy heart," she said in a statement.
Emerson is considered one of the most moderate members of the Republican caucus. Her departure reflects the continued polarization of the House, some observers said.
"This is not a comfortable body anymore for people like Jo Ann Emerson," said Norm Ornstein, a political scholar with the American Enterprise Institute. "So leaving for a good job outside Congress is a logical, if depressing, step."
Colleagues paid tribute to her throughout the day.
"Jo Ann is a middle-of-the-road moderate -- an approach I know firsthand can sometimes be a lonely one," said a statement from Sen. Claire McCaskill, a Democrat.
"I know that Jo Ann will continue serving Missourians in (her) new role," said GOP Sen. Roy Blunt.
Emerson's predecessor was her husband, Bill, who died in office.
It wasn't immediately clear why Emerson waited until just after the November election to make her decision.
Gov. Jay Nixon, who also praised Emerson on Monday, must now call a special election for the seat. A spokesman said the governor hasn't picked a date.
There won't be a primary. The parties will pick nominees, and candidates are already lining up. Among those thinking about the race are Lt. Gov. Peter Kinder, former Senate candidate Sarah Steelman and Republican Party director Lloyd Smith.