ST. LOUIS — Rep. Cori Bush confirmed Tuesday that the U.S. Department of Justice is investigating her campaign’s spending on security services. In a statement, Bush said she was “fully cooperating” with investigators. The statement followed reports by the New York Times and other news outlets that said the Justice Department had subpoenaed records from her congressional office. Bush’s spending on security services — a topic previously reported on by the Post-Dispatch — has been the subject of several ethics complaints. Labeling those allegations as “baseless” and “frivolous,” the St. Louis Dem…