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The longest serving woman in Congress in U.S. history is ready to retire. Maryland Democrat Barbara Mikulski will not seek a sixth term in the Senate in 2016.

Mikulski made the announcement at a news conference in the Fells Point neighborhood in Baltimore Monday morning.

"I am here today ... to announce I will not be seeking a sixth term in the United States Senate," Mikulski said. "This is a hard decision to make."

"Do I spend my time raising money or spend my time raising hell?" the Maryland Democrat said is a question that factored into her decision.

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Mikulski, whose direct and feisty character paved the way for women who joined the male-dominated Senate, joined the upper chamber in 1987 after ten years in the U.S. House. The 78-year old intends to serve out the remainder of her current term until January 2017.

Mikulski is currently the top Democrat on the powerful Appropriations Committee. She was the first woman to chair the committee responsible for determining and allocating government funding when she took the gavel in December of 2012.

Her retirement could open up the possibility of a contested race in the predominantly blue state, especially in the Democratic primary. Maryland voted for President Barack Obama by 62 percent in both 2008 and 2012 but just elected a Republican for governor in 2014.

It is home to powerful and dynamic politicians who could decide to run for the open seat. On the Democratic side, House Minority Whip, the second highest Democrat in the House, Steny Hoyer, represents the state as does Rep. Chris Van Hollen, who is the top Democrat on the House Budget Committee and a member of House Leadership. Rep. Donna Edwards, the first African American woman from Maryland elected to the House is a possibility and so is Anthony Brown, former Lt. Governor, who surprisingly lost the race for governor in 2014 in what became a bad year to run as a Democrat. Baltimore Mayor Stephanie Rawlings-Blake could consider a run, too, as could Heather Mizeur, former member of House of Delegates and former candidate for governor.

It's also worth nothing that former Maryland Governor Martin O'Malley is considering a presidential run.

On the Republican side, Rep. Andy Harris is a potential contender. National Republican Senatorial Committee spokesperson Andrea Bozek noted that Republicans will be watching what could be the Democrats' "bloody primary."

“After winning the Governor’s race in 2014, there's no question that an open Senate seat in Maryland instantly becomes a top pickup opportunity for Republicans," Bozek said. "While Democrats get ready for a bloody primary, we will have a top recruit waiting for whoever emerges."

Before joining Congress, Mikulski was a social worker. As a pioneer in the old-boys club, she is known for advocating for collegiality among women in the Senate, organizing a monthly dinner for women senators.

A record number of women - 20 - currently serve in the Senate.