WASHINGTON -- When President Donald Trump's former campaign manager, Corey Lewandowski, appeared in January before the House Intelligence Committee investigating Russian political interference, he refused to answer questions about his conversations with Trump after he was fired by the future president in June 2016.
The Republicans running the panel responded not with a subpoena, which Congress can use to compel testimony. They invited Lewandowski to return when he was ready, and he's scheduled to testify again on Thursday.
Stephen K. Bannon, the former White House chief strategist; Donald Trump Jr., the president's eldest son; and Hope Hicks, the outgoing communications director, also have declined to discuss certain topics in closed-door House committee hearings.
Over in the Senate, top Trump administration intelligence and law enforcement officials, most notably Attorney General Jeff Sessions, have refused to discuss their private conversations with Trump, at least in public hearings, regarding Russia and other issues.
Most of the conflicts over congressional testimony have revolved around executive privilege, the president's legal authority to keep some conversations and other material secret to protect internal deliberations. Although the White House hasn't formally invoked the privilege, Trump's current and former aides said they would not answer questions to protect the president's right to cite the privilege later should he seek to do so.
Legal experts said the White House had significantly broadened the traditional use of executive privilege to direct individuals to avoid answering questions about specific conversations with the president.
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The Trump White House is "preventing any testimony from people on the grounds that something, at some point, is potentially covered by executive privilege," said Mark J. Rozell, a professor at George Mason University who has studied the presidency.
"Then it becomes a blanket protection to prevent any and all questions from current and former staff, which is an almost breathtaking notion of executive privilege," he added.
Robert Bauer, who served as White House counsel under President Barack Obama, said the Trump administration "is attempting something quite new."
"Normally, an administration advances a claim of executive privilege, then negotiates around it to accommodate the Congress without forcing the conflict to outright confrontation," Bauer said.