“Based on information learned during discovery, the deposition of Mrs. Clinton may be necessary,” wrote Michael Bekesha, counsel for Judicial Watch. (Melina Mara/The Washington Post)

A conservative legal advocacy group submitted plans Tuesday to question under oath seven current and former top State Department officials and aides to Democratic presidential contender Hillary Clinton — but not Clinton herself at this point — about her use of a private email server when she was secretary of state.

Judicial Watch said its deposition plan includes Cheryl D. Mills, who was Clinton’s chief of staff at State; Huma Abedin, a top aide who served as Mills’s deputy and who now is vice chairman of Clinton’s presidential campaign; and Bryan Pagliano, a Clinton staff member during her 2008 presidential campaign who helped set up the private server.

U.S. District Judge Emmet G. Sullivan of Washington granted a request on Feb. 23 for legal discovery by Judicial Watch, which seeks to determine whether Clinton’s email arrangement thwarted federal open-records laws. After his order, Sullivan directed Judicial Watch to file a detailed plan about how it intended to proceed.

The submitted plan can be contested by lawyers from the Justice and State departments and is subject to approval by Sullivan.

Sullivan set an April 12 deadline for filings by the two sides, meaning that questioning of key Clinton aides could take place as she tries to secure the Democratic nomination and turn to the November general election.

“Based on information learned during discovery, the deposition of Mrs. Clinton may be necessary,” wrote Michael Bekesha, counsel for Judicial Watch. “If Plaintiff believes Mrs. Clinton’s testimony is required, it will request permission from the Court at the appropriate time.”

Judicial Watch also said it wants to question Undersecretary for Management Patrick F. Kennedy; Stephen D. Mull, executive secretary from June 2009 to October 2012; Lewis A. Lukens, executive director of the executive secretariat from 2008 to 2011; and Donald R. Reid, senior coordinator for security infrastructure in the bureau of diplomatic security.

A Justice Department spokesman declined to comment.

Clinton campaign spokesman Brian Fallon said, “This is the same right-wing organization that has been repeatedly attacking the Clintons without success since the 1990s, and they are clearly going to pull out all the stops to try to hurt the secretary’s presidential campaign.”

The Judicial Watch lawsuit came over a May 2013 request for information about Abedin’s employment arrangement. For six months in 2012, Abedin was employed simultaneously by the State Department, the Clinton Foundation, Clinton’s personal office and a private consulting firm connected to the Clintons.

In his February ruling, Sullivan criticized the government for what he called “a constant drip” of piecemeal disclosures and a “staggering” amount of resources devoted to a situation in which private counsel for former federal employees — Clinton and Abedin — decided what government records to disclose.

“It just boggles the mind that the State Department allowed this circumstance to arise in the first place. It’s just very, very, very troubling,” Sullivan said.

Sullivan said there was sufficient basis to show that senior department officials knew of Clinton’s server arrangement from the time she took over at State in January 2009, citing an email chain among Kennedy, Lukens, Mills and others regarding setting up a computer in Clinton’s office so that she could check her “off network” email.

Sullivan also noted email traffic among Abedin, Mull, Mills, Kennedy and others discussing communication problems, in which Mull suggested that Clinton be issued a State Department BlackBerry that would protect her identity but be subject to public-records requests.

“How on earth can the Court conclude that there’s not, at a minimum, a reasonable suspicion of bad faith regarding the State Department’s response to this FOIA request?” Sullivan said. “It appears that no one took any steps to ensure that agency records on Clintonemail.com were secured within the State Department’s record systems so that FOIA requests received during the former secretary’s tenure would be responded to appropriately.”

Judicial Watch said it intended to seek answers about department officials’ creation, maintenance, support or awareness of Clinton’s email system; any instructions given to department workers about communicating by email with Clinton and Abedin; and any inquiries into or discussions about disclosing Clinton’s use of the system.

The group also said it would ask the department to identify who handled requests for email records from the secretary’s office, inventoried Clinton’s and Abedin’s information, or used an account on Clinton’s email server for official business.