One of the lead House investigators into the Benghazi terrorist attack called for former Secretary of State Hillary Clinton to testify before Congress about information provide by State Department whistleblowers, adding that he would support issuing a subpoena if she refuses.

“I would hope that she would step up and help us out,” Rep. Jason Chaffetz, R-Utah, replied when Charlie Rose asked him if he wants the House Oversight and Government Reform Committee to subpoena Clinton. Chaffetz emphasized that the committee is not yet ready to issue such a summons, but noted that “we do have whistleblowers stepping up, [so] I think we’re going to get serious about forcing people legally to [testify].”

Chaffetz — sounding as if he wanted to avoid saying anything that would seem to vindicate critics who dismiss the current Benghazi investigation as a witch-hunt designed to hurt Clinton’s ability to win the presidency in 2016 — said that if Clinton will not voluntarily appear, then “at some point, yeah, I’ll be supportive of [a subpoena].”

The lawmaker explained that, among other things, he’d like to hear Clinton describe her conversation with deputy chief of mission Gregory Hicks, to whom she spoke by phone at 2 a.m. local time after the first assault on the U.S. mission in Benghazi.

Hicks also testified that he was instructed not to meet with Chaffetz when he traveled to Tripoli to investigate the Benghazi attacks. He said that Clinton chief of staff Cheryl Mills berated him for having a classified, one-on-one meeting with Chaffetz. Mills wanted the Chaffetz meeting to take place only in the company of a State Department attorney.

Clinton appeared before the House and Senate Foreign Relations Committees to testify about the attacks in January.