Updated: 4:58 p.m. ET
Democratic Nebraska Senator Ben Nelson will be retiring from the Senate after the end of his second term, he announced on Tuesday.
In a video statement released Tuesday afternoon, the two-term senator confirmed his decision not to run for re-election, citing a desire to spend more time with his family and "look for new ways to serve our state and nation."
"There is much more that needs to be done to keep America strong. And while I relish the opportunity to undertake the work that lies ahead, I also feel it's time for me to step away from elective office, spend more time with my family, and look for new ways to serve our state and nation," Nelson said. "Therefore, I am announcing today that I will not seek reelection. Simply put: It is time to move on."
The 70-year-old conservative Democrat's retirement will create a new challenge for Democrats hoping to maintain the seat in the solidly red state.
Nelson, who previously served as Nebraska's governor for two terms, was expected to face a difficult re-election fight himself despite extensive Democratic efforts aimed at improving his image among his constituents. He has more than $3 million cash on hand, which could be redirected to another candidate.
Currently, Nebraska Attorney General Jon Bruning, Nebraska state Sen. Deb Fischer and state Treasurer Don Stenberg are all contending for the Republican nomination.
While the Democratic field for the race has yet to be determined, there has been talk that former Democratic Senator and Governor Bob Kerrey could join the fray. Kerrey was a popular politician in the state, but he has not been on a ballot there since 1994. From 2001 to 2010, he served as the president of The New School in New York City.
Republicans need to gain a net four seats in 2012 to retake control of the currently Democratic-led Senate.
Larry Sabato, a political scientist at the University of Virginia, expressed skepticism that Kerrey would run for the seat, and called Nelson's retirement a "blow" to Democrats.
"This is another blow to Democratic hopes of retaining control of the senate. His seat is very, very likely to switch to the Republicans now," Sabato told CBS News.
"They really don't have anybody to run," he added. "They hope that somebody like former senator Bob Kerrey will show up at the doorstep, but it's highly unlikely."
In a Wednesday statement, President Obama thanked the senator and praised his commitment to bipartisanship.
"I want to thank Senator Nelson for his years of service representing the people of Nebraska, first as Governor and then for more than a decade in the United States Senate," Mr. Obama said in the statement. "Over the course of his career, Ben's commitment to working with both Democrats and Republicans across a broad range of issues is a trait far too often overlooked in today's politics. Michelle and I commend Ben for his service, and wish him and his family well in the future."