By Chris Casteel, Washington BureauWASHINGTON — State Rep. T.W. Shannon said Wednesday that he would prefer outside groups stick to the issues in the U.S. Senate race. “As we have seen in Senate races across the country, there likely will be many groups weighing in on both sides of this race,” Shannon said in a statement issued by his campaign. “I hope everyone will agree that keeping the advertising focused on issues and records will best serve the people of Oklahoma as they determine who their next U.S.