Democratic Sen. Joe Manchin of West Virginia said on Sunday that he will run for re-election in 2018 rather than make a return bid for governor next year, saying he believes he can have the greatest impact by staying in Washington.

"This place may not be working now, but I'm not going to stop fighting to make it work," Manchin said in a statement.

Manchin is West Virginia's only Democrat in Congress. He was a two-term governor when he won a special election in November 2010 to fill the vacancy left by the death of Democratic Sen. Robert Byrd.

He won a full six-year term in 2012 with 61 percent of the vote -- while President Barack Obama lost every West Virginia county against Mitt Romney.

The political hostility and lack of bipartisanship in Washington had led the centrist to consider leaving.

"I will admit that it has been a harder transition than I had expected, but I believe that, after five years, we are beginning to make a difference," Manchin said. "We are simply bringing a greater sense of bipartisanship and commitment to working together for the good of the American people. It is because of that optimism that I have decided to continue serving the people of West Virginia in the United States Senate."

He told CBS' "Face the Nation" on Sunday that he thinks "we've made some inroads" in the Senate "to where we're willing to put the country first."

Manchin has sought to work with Republicans, including unsuccessful legislation in 2013 to expand background checks on firearm purchases as a way of curbing gun violence. He has co-chaired a group called No Labels, which promotes bipartisanship and problem-solving.

Republicans Attorney General Patrick Morrisey, state Senate President Bill Cole and U.S. Rep. David McKinley have expressed interest in running for governor, along with Democratic state Senate Minority Leader Jeff Kessler. Kessler has opened a pre-candidacy campaign account for governor.