CHARLESTON, W.Va. — West Virginia Sen. Joe Manchin says he’s staying in the U.S. Senate and won’t run for governor. The 72-year-old Manchin announced his decision on Tuesday after months of reflection. It means Manchin will steer clear of a potential showdown with incumbent Republican Gov. Jim Justice, who already has announced he’s seeking re-election. Earlier this year, Manchin became the top Democrat on the Senate Energy Committee, giving the coal-state lawmaker a prominent position to shape policy. But Manchin says he has become frustrated with a lack of Senate productivity and bipartisanship. Manchin was elected governor in 2004 and re-elected in 2008 before winning a special election in the Senate following the June 2010 death of Robert C. Byrd. Manchin won a second six-year term in the Senate last November.