U.S. Sen. Amy Klobuchar filed paperwork for her campaign for Minnesota governor Thursday, weeks after Gov. Tim Walz ended his campaign for a third-term amid a widening scandal of fraud in state-run social service programs. “This is a preliminary step necessary for any candidate considering a run,” according to a person close to the senator who spoke on condition of anonymity because they were not authorized to speak publicly. “The senator will make an announcement of her plans in the coming days.” Klobuchar, 65, is a proven vote-getter, having been reelected three times since first winning her seat in 2006....