Senator Barbara A. Mikulski announced her retirement Monday in Baltimore.
Mikulski, speaking at the podium by herself, said she spent considerable time thinking about how she wanted to spend the next two years and ultimately decided she didn't want to run another campaign.
"Do I spent my time raising money or raising hell to meet your day-to-day needs? Do I spend time focusing on my election or the next generation?" Mikulski said. "The more I thought about it, the more the answer became really clear.
"That's why I'm here to announce I won't be seeking a 6th term as a United States senator for Maryland," she said.
Mikulski, often described as "tough as nails," became emotional as she recalled her years growing up in Baltimore and thanked Maryland voters for honoring her "with your confidence and trust."
Mikulski said she is eager to help elevate the next generation of Democrats, but declined to say whether there were any particular potential candidates she thought might be good for the job.
"Maryland has a lot of talent," Mikulski quipped. "They'll be telling you about it in the next 10 minutes."
The Democrat and the longest-serving woman in the history of Congress addressed the media at 11 a.m. in Fells Point, after promising an "important announcement about her future plans."
Mikulski, 78, is a Highlandtown native and Maryland's senior senator. She began in 1976 in the House of Representatives. She has served in the Senate since 1987, recently heading the Appropriations Committee, and would have been up for re-election next year.
Senator Jon Tester, Chair of the Democratic Senatorial Campaign Committee, said he is confident another Democrat would emerge "and make Barbara Mikulski proud."
In a statement, Tester said: "Barbara Mikulski is as well-respected of a legislator as anyone I've served with in the U.S. Senate and it has been my privilege to work with her. Her unyielding commitment to the people of Maryland is matched only by the sheer number of lives she's inspired over her long career. Barbara is a force of nature on the Senate floor and she will be missed both by her colleagues and her constituents.
Joe Cluster, executive director of the Maryland Republican party said Mikulski's retirement shakes up Maryland politics. The party expects to be able to contend in congressional districts they haven't been able to compete in for years when Democratic sitting congressmen run for Mikulski's seat.
Cluster said he hasn't expressly heard interest from any candidates Monday, but expects Ehrlich and former Lt. Gov. Michael Steele to be contemplating it.
"I look at this from the outside. I look at what Larry Hogan did to win," Cluster said. He added that its possible that a Republican from the business community could emerge to seek the seat, though he didn't offer any names.
Hogan, meanwhile, doesn't have any interest in running for the seat, and neither does Democratic Comptroller Peter Franchot, according to sources familiar with their plans.
Baltimore Sun reporters Yvonne Wenger, Erin Cox, Liz Bowie and Sean Welsh contributed to this story.