WASHINGTON — Gen. Carter F. Ham, who led the United States Africa Command on the night of the attack on the American diplomatic compound in Benghazi, Libya, has been interviewed at least nine times by investigators scrutinizing the events in 2012 that led to the deaths of Ambassador J. Christopher Stevens and three other Americans.

But more than two years after House Republicans created the Select Committee on Benghazi, General Ham has yet to appear before that panel. He was finally supposed to do so on Thursday, but Republicans suddenly postponed the session until June 8, citing scheduling conflicts.

Whether by diligence or design, the committee’s grindingly slow pace has put it on track to deliver a final report shortly before the presidential nominating conventions in July, or even as late as the weeks before the November election — both points at which it could inflict maximum political damage on Hillary Clinton, who has been a central focus of the investigation since its inception.

Even some Republicans say the sluggishness of the committee, which has long been under fire from Democrats who describe it as a partisan witch hunt, risks feeding its reputation as an exercise meant to harm Mrs. Clinton’s presidential campaign. It also illustrates how a committee created to get at the truth of a terrorist attack that killed four Americans has expanded in multiple directions but could fail to come up with significant new information.