Clinton has agreed to testify to the House panel investigating the Benghazi attack and could appear later this month. She has refused a request to testify a second time before the panel.

Johnson raised a number of questions about Clinton, including why she didn’t immediately call survivors of the 2012 attack on the U.S. compound in Benghazi and why security wasn’t raised before the attack.

“You could have told the American people the truth,” Johnson said Tuesday during an interview on MSNBC’s “Morning Joe.” “And bottom line is, now is the time for Secretary Clinton to tell the America the truth.”

Johnson, who faces a difficult reelection race next year, argued that the State Department did not respond to repeated requests to increase security at the compound.

“Those requests went — not only went unanswered, they actually ramped down security basically to comply with their narrative that all was well, that their strategy was working. Nothing could be further from the truth,” he said.

Four Americans, including the U.S. ambassador to Libya, were killed in the attack.

Johnson, a member of the Senate Foreign Relations Committee, had a memorable exchange with Clinton in January 2013, when she appeared before that panel and cut off his line of questioning.

“With all due respect, the fact is we had four dead Americans,” Clinton said at the time. “Was it because of a protest or was it because of guys out for a walk last night who decided to kill some Americans? What difference, at this point, does it make?”

Clinton’s outburst buoyed her supporters and other Democrats, but Republicans zeroed in on the “what difference, at this point, does it make” to cast her as out of touch.

On Tuesday, Johnson downplayed the significance of the argument, noting that others have labeled it a “heated exchange.”

“Not from my part; I was just asking some pretty simple questions,” said Johnson.