On Thursday, a US House committee investigating Hillary Clinton's private e-mail server voted along party lines to hold the Democratic presidential candidate's former IT aide in contempt of Congress.

Bryan Pagliano, the former State Department IT technician who helped set up Clinton's private e-mail server when she was secretary of state, did not appear before the House Oversight and Government Reform Committee during its hearing investigating the server. However, Pagliano was subpoenaed.

"Subpoenas are not optional," Committee Chairman Jason Chaffetz (R-Utah) said Thursday. "Mr. Pagliano is a crucial fact witness in this committee's investigation of former Secretary of State Hillary Clinton's use of a private server to conduct government business."

The committee's resolution, adopted on a party-line vote of 19-15, must be approved by the House. If approved, it would be up to the District of Columbia US attorney to decide whether to prosecute.

Pagliano had invoked his constitutional right against compelled self-incrimination last week when subpoenaed to testify on the same issue before the House Select Committee on Benghazi.

Pagliano's attorneys wrote Chaffetz late Wednesday to say that Pagliano "will continue to assert his Fifth Amendment rights and will decline to answer any questions put to him by your Committee." The lawyers added: "In an effort to resolve this matter, Mr. Pagliano has offered to assert his rights on the record before this Committee in Executive Session. You have flatly refused that offer and continue to insist that Mr. Pagliano appear in a public session where his further and repeated assertion of his constitutional right not to testify can be videotaped and broadcast."

House Democrats said the contempt resolution was designed to hurt Clinton's presidential bid against GOP rival Donald Trump.

"Where is our investigation of Donald Trump? His potentially fraudulent business practices?" asked Rep. Elijah E. Cummings, the ranking Democrat on the committee. "This is an abuse of authority and taxpayer dollars to inappropriately affect the presidential election."

Pagliano received limited immunity from prosecution as part of the FBI investigation into Clinton's private e-mail servers. The bureau found that Clinton was "extremely careless," but no criminal prosecution was recommended. Republicans were outraged over the decision because some e-mails contained classified data that was hosted on a private server at her New York residence.

For a closer examination of Pagliano's role, read our previous coverage detailing the evolution of Clinton's server. It began on a Power Mac, shifted to a Dell PowerEdge 2900 running Windows Server and Microsoft Exchange, and then moved to a Dell PowerEdge 1950 running Blackberry Enterprise Server (BES).