South Dakota state Rep. Stace Nelson (R) met with a handful of national conservative groups last week in Washington — an indication they continue to search for a challenger to former Gov. Mike Rounds (R) in the state’s open Senate race. The Republican primary field is already wide, and a bruising contest could jeopardize a pickup that is crucial to GOP efforts to take back the Senate in 2014. Nelson met with Sen. Ted Cruz’s (R-Texas) office, Americans for Tax Reform’s Grover Norquist and the Club for Growth. “To say things went well is an understatement,” Nelson told The Hill....