Held in the ornate room that is home to the House Ways and Means Committee, the marathon hearing began at 10 a.m. and, with breaks, lasted until 9 p.m. It provided Republicans with a national audience as they questioned Mrs. Clinton, often using her own words from thousands of pages of emails obtained by the committee. But it also gave Mrs. Clinton her first opportunity since early 2013 to respond directly to her fiercest critics, and she used the platform to offer lengthy explanations of her diplomatic efforts around the world and her actions before and after the Benghazi attacks.

Perhaps stung by recent admissions that the pursuit of Mrs. Clinton’s emails was politically motivated, Republican lawmakers on the panel for the most part avoided any mention of her use of a private email server. Still, Representative Jim Jordan of Ohio did raise the issue late in the hearing, accusing her of repeatedly changing her account of the server and why she had used it. In a heated exchange, Mrs. Clinton repeated that she had made a mistake in using a private email account, but maintained that she had never sent or received anything marked classified and had sought to be transparent by publicly releasing her emails.

But committee Republicans focused mostly on accusations that Mrs. Clinton had ignored security needs in Benghazi in the months before the attacks, a charge she repeatedly rejected.

Throughout the day, Democrats on the committee portrayed Republicans as the leaders of a partisan crusade against Mrs. Clinton, while Republicans responded angrily that Democrats were seeking to block a legitimate inquiry into fatal security lapses at an American diplomatic outpost. Shortly before the committee broke for lunch, a shouting match erupted between Mr. Gowdy and two Democrats, Adam B. Schiff and Elijah E. Cummings, over the focus on Mrs. Clinton’s email exchanges with Sidney Blumenthal, a former aide to her husband and a friend.