In this Aug. 28, 2015, file photo, Democratic presidential candidate Hillary Rodham Clinton, addresses the summer meeting of the Democratic National Committee in Minneapolis. The State Department made public roughly 7,121 pages of Clinton's e-mails late Monday night, including 125 emails that were censored prior to their release because they contain information now deemed classified. (AP Photo/Jim Mone) (Jim Mone/AP)

The presidential campaign of Democratic front-runner Hillary Rodham Clinton expressed disappointment that a former computer staffer is refusing to answer questions before Congress about her private e-mail system, saying Clinton had urged all her staff to cooperate.

“We have been confident from the beginning that Hillary Clinton’s use of a personal e-mail was allowed and that she did not send or receive anything marked classified, facts confirmed by the State Department and the Inspector General,” campaign spokesman Nick Merrill said in a statement.

“She has made every effort to answer questions and be as helpful as possible, and has encouraged her aides, current and former, to do the same, including Bryan Pagliano,” Merrill added. “In fact, two of those aides are due to testify this week, and she is eager to testify in a public hearing in October.”

Pagliano, who helped Clinton manage a private e-mail server at her home while she was secretary of state, this week rebuffed a subpoena to testify before a House committee investigating fatal terrorist attacks on two U.S. compounds in Benghazi, Libya, in September 2012 and now Clinton’s unusual private e-mail system.

In a letter Monday, Pagliagno’s lawyer told Rep. Trey Gowdy (R-S.C.), the committee chairman, that Pagliano would not answer any questions if forced to appear and would instead assert his constitutional right not to do so. His lawyer cited an ongoing FBI investigation into whether Clinton’s e-mail arrangement — using a private e-mail account and server exclusively for all State Department business — compromised national security information.

The State Department released more than 7,000 pages of e-mails sent or received by Hillary Clinton as part of an ongoing probe into her private e-mail server. The Post’s Anne Gearan discusses their content and what these releases mean to Clinton’s 2016 presidential campaign. (Julie Percha/The Washington Post)

The Fifth Amendment allows people to refuse to answer questions in any proceeding, civil or criminal, to protect themselves from self-incrimination. Many lawyers advise clients to take the Fifth in sensitive probes, even when there is no indication they are involved in any misconduct or crime, out of a concern that they could get into trouble simply by misspeaking.

“While we understand that Mr. Pagliano’s response to this subpoena may be controversial in the current political environment, we hope that the members of the Select Committee will respect our client’s right to invoke the protections of the Constitution,” his attorney, Mark MacDougall, wrote. “As the Supreme Court has made clear, ‘One of the Fifth Amendment’s basic functions . . . is to protect innocent men . . . who otherwise might be ensnared by ambiguous circumstances.’”

Refusing to answer Congress’s questions is more politically problematic for close Clinton aides who may play a role in her campaign or in her administration if she is elected president.

Cheryl Mills, Clinton’s chief of staff when she headed the State Department, is scheduled to testify in a closed hearing with the House Benghazi committee Thursday. Jake Sullivan, Clinton’s deputy chief of staff during that period and current foreign policy adviser to her campaign, is scheduled to answer questions Friday.

Clinton’s e-mail arrangement, first revealed in March as a result of the committee’s insistence on getting copies of her e-mails before and after the 2012 Benghazi attacks, continues to dog her politically. She originally asserted that she never sent or received classified e-mails and that was standard procedure to use her personal e-mail system as she did. But new information and the release of many of her work e-mails have cast doubt on some of her claims.

Thousands of e-mails that have been released by the State Department as part of a public records lawsuit show Clinton herself writing at least six e-mails containing information that has since been deemed classified. Large portions of those e-mails were redacted before their release, on grounds that their publication could harm national security.

State Department spokesmen have repeatedly refused over two days to answer whether that information was classified at the time Clinton wrote her e-mails — that is, whether she mishandled sensitive material and should have discussed it on a secure, classified government e-mail system.