Senate Republicans are now privately threatening to derail the confirmation of key Obama administration nominees for top legal positions by linking the votes to suppressing critical torture memos from the Bush era. A reliable Justice Department source advises me that Senate Republicans are planning to “go nuclear” over the nominations of Dawn Johnsen as chief of the Office of Legal Counsel in the Department of Justice and Yale Law School Dean Harold Koh as State Department legal counsel if the torture documents are made public. The source says these threats are the principle reason for the Obama administration’s abrupt pullback last week from a commitment to release some of the documents. A Republican Senate source confirms the strategy. It now appears that Republicans are seeking an Obama commitment to safeguard the Bush administration’s darkest secrets in exchange for letting these nominations go forward.

Not a single Republican indicated an intention to vote for Dawn Johnsen, while Senator John Cornyn of Texas was described as “gunning for her,” specifically noting publication of the torture memos.

Barack Obama entered Washington with a promise of transparency. One of his first acts was a presidential directive requiring that the Freedom of Information Act, a near dead letter during the Bush years, was to be enforced according to its terms. He specifically criticized the Bush administration’s practice of preparing secret memos that determined legal policy and promised to review and publish them after taking office.

But in the past week, questions about Obama’s commitment to transparency have mounted. On April 2, the Justice Department was expected to make public a set of four memoranda prepared by the Office of Legal Counsel, long sought by the American Civil Liberties Union and other advocacy organizations in a pending FOIA litigation. The memos, authored by then-administration officials and now University of California law professor John Yoo, federal appellate judge Jay Bybee and former Justice Department lawyer Stephen Bradbury, apparently grant authority for the brutal treatment of prisoners, including waterboarding, isolated confinement in coffin-like containers, and “head smacking.” The stakes over release of the papers are increasingly high. Yoo and Bybee are both targets of a criminal investigation in a Spanish court probing the torture of five Spanish citizens formerly held in Guantánamo; also named in the Spanish case are former Attorney General Alberto Gonzales and three other Bush lawyers. Legal observers in Spain consider the Bush administration lawyers at serious risk of indictment, and the memos, once released, could be entered as evidence in connection with their prosecution. Unlike the torture memos that are already public, these memos directly approve specific torture techniques and therefore present a far graver problem for their authors.

The release of the memos that the Senate Republicans want to suppress was cleared by Attorney General Eric Holder and White House counsel Greg Craig, and then was stopped when “all hell broke loose” inside the Obama administration, according to an article by Newsweek reporter Michael Isikoff. Newsweek attributes internal opposition to disclosure of the Bush-era torture memos to White House counterterrorism adviser and former CIA official John O. Brennan, who has raised arguments that exposure of the memoranda would run afoul of policies protecting the secrecy of agency techniques and has also argued that the memos would embarrass nations like Morocco, Jordan, Pakistan, Tunisia and Egypt, which have cooperated closely with the CIA in its extraordinary renditions program. Few informed independent observers, however, find much to credit in the Brennan objections because the techniques are now well-known, as is the role of the cooperating foreign intelligence services—any references to which would in any event likely be redacted before the memoranda are released. Moreover, the argument that the confidence of those engaged in torture—serious criminal conduct under international and domestic law—should be kept because they would be “embarrassed” if it were to come out borders on comic.

The Justice Department source confirms to me that Brennan has consistently opposed making public the torture memos—and any other details about the operations of the extraordinary renditions program—but this source suggests that concern about the G.O.P.’s roadblock in the confirmation process is the principle reason that the memos were not released. Republican senators have expressed strong reservations about their promised exposure, expressing alarm that a critique of the memos by Justice’s ethics office (Office of Professional Responsibility) will also be released. “There was no ‘direct’ threat,” said the source, “but the message was communicated clearly—if the OLC and OPR memoranda are released to the public, there will be war.” This is understood as a threat to filibuster the nominations of Johnsen and Koh. Not only are they among the most prominent academic critics of the torture memoranda, but are also viewed as the strongest advocates for release of the torture memos on Obama’s legal policy team.

A Republican Senate staffer further has confirmed to me that the Johnsen nomination was discussed at the last G.O.P. caucus meeting. Not a single Republican indicated an intention to vote for Dawn Johnsen, while Senator John Cornyn of Texas was described as “gunning for her,” specifically noting publication of the torture memos.

No decision was taken at that Republican caucus meeting whether to filibuster or not, though Cornyn was generally believed to support filibustering Johnsen and potentially other nominees. Johnsen has met recently with moderate Republican Senators Susan Collins of Maine and Arlen Specter of Pennsylvania, both of whom are being lobbied heavily by colleagues and religious right groups to oppose her nomination.

Both Koh and Johnsen are targets of sustained attacks coming from right-wing lobbying groups. The Daily Beast previously reviewed the attacks on Johnsen, while Slate’s Dahlia Lithwick has catalogued the recent attacks on Koh. Former Bush administration Solicitor General Ted Olson recently endorsed the Koh nomination, calling the Yale dean “a man of great integrity.” But connecting the Obama nominations to the Bush torture memos escalates the conflict toward a thermonuclear level.

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Scott Horton is a law professor and writer on legal and national-security affairs for Harper's magazine and The American Lawyer, among other publications.