WASHINGTON — With a vote looming to hold Attorney General Eric Holder in contempt of Congress, a House committee chairman is challenging President? Barack Obama's claim of executive privilege, invoked to maintain secrecy for some documents related to a failed gun-tracking operation.

Obama's claim broadly covers administration documents about the program called Operation Fast and Furious, not just those prepared for the president. But Rep. Darrell Issa, R-Calif., chairman of the House Oversight and Government Reform Committee that recommended the contempt charge, maintains the privilege is reserved for documents to and from the president and his most senior advisers.

Behind the legal argument is a political dispute. House Republican leaders are pressing for a contempt vote against Holder that is tentatively scheduled for Thursday, the same day the Supreme Court will rule on the legality of the nation's health care law.

Rep. Steny Hoyer of Maryland, the House Democrats' chief head counter, said he expected some Democrats to follow the National Rifle Association's call for a "yes" vote on contempt. The NRA has written to all members of Congress, saying the White House wanted to use the Operation Fast and Furious gun-tracking operation to advance a gun control agenda.

Hoyer would not give a number of potential defectors.

At a news conference, civil rights leaders said Holder is being targeted by Republicans because he has aggressively enforced laws guaranteeing the right to vote.

The attorney general's opponents want to "put a cloud over his head" and they want to see "if they can slow him down," said the Rev. Al Sharpton. Among the other participants were the heads of the Leadership Conference on Civil and Human Rights, the Urban League, the NAACP and the National Council of La Raza.

In a letter to the president dated Monday and made public Tuesday, Issa cited an appellate court decision to back his claim and questioned whether Obama was asserting a presidential power "solely for the purpose of further obstructing a congressional investigation."

White House Spokesman Eric Schultz said Tuesday that Issa's analysis "has as much merit as his absurd contention that Operation Fast and Furious was created in order to promote gun control. Our position is consistent with executive branch legal precedent for the past three decades spanning administrations of both parties."

Courts have routinely "affirmed the right of the executive branch to invoke the privilege even when White House documents are not involved," Schultz said.

Some experts agree with the president's view that all executive branch documents are protected from disclosure. Ohio State University law professor Peter Shane, a specialist in presidential power, says executive privilege historically covers documents generated anywhere in the executive branch.

Holder's offer last week to turn over some documents – the Justice Department has provided 7,600 records so far – was rejected by Issa because he contended the attorney general was demanding an end to the committee's investigation.

Ironically, the documents at the heart of the current argument are not directly related to the workings of Operation Fast and Furious, which allowed guns to "walk" from Arizona to Mexico in hopes they could be tracked.

Rather, Issa wants internal communications from February 2011, when the administration denied knowledge of gun-walking, to the end of the year, when officials acknowledged the denial was in error. Those documents covered a period after Fast and Furious was shut down.

In Fast and Furious, agents of the federal Bureau of Alcohol, Tobacco, Firearms and Explosives in Arizona abandoned the agency's usual practice of intercepting all weapons they believed to be illicitly purchased. Instead, the goal of gun-walking was to track such weapons to high-level arms traffickers who long had eluded prosecution and to dismantle their networks.

Gun-walking long has been barred by Justice Department policy, but federal agents in Arizona experimented with it in at least two investigations during the George W. Bush administration before Fast and Furious. These experiments came as the department was under widespread criticism that the old policy of arresting every suspected low-level "straw purchaser" was still allowing tens of thousands of guns to reach Mexico. A straw purchaser is an illicit buyer of guns for others.

The agents in Arizona lost track of several hundred weapons in Operation Fast and Furious. The low point of the operation came in Arizona in 2010, when Border Patrol Agent Brian Terry was killed in a firefight with a group of armed Mexican bandits and two guns traced to the operation were found at the scene.

Issa, in his letter to the president, wrote, "Courts have consistently held that the assertion of the constitutionally-based executive privilege ... is only applicable ... to documents and communications that implicate the confidentiality of the president's decision-making process."

The letter said that while the privilege covers only the president and his advisers, it is a qualified privilege that can be overcome by a showing of the committee's need for the documents.

Shane, the Ohio State professor, said: "Executive privilege is really an umbrella concept that encompasses a variety of privileges. History's most famous claim of executive privilege – President Richard Nixon's unsuccessful attempt to withhold the Watergate tapes – was an example of `presidential privacy privilege.' That privilege covers executive communications when the president is involved."

He said the executive branch historically claims a much broader privilege, the so-called deliberative privilege. That claim tries to protect documents generated anywhere in the executive branch that embody only the executive's internal deliberations, not final policy decisions. The current dispute involves deliberative privilege, he said.

Issa quoted from a 1997 case in the U.S. Court of Appeals for the District of Columbia Circuit in which the court said the privilege should not extend to staff outside the White House in executive branch agencies.

Rather, the court said, it should apply only to "communications authored or solicited and received by those members of an immediate White House adviser's staff" with responsibility for formulating advice for the president.

However, the case which Issa repeatedly cited in his letter distinguishes carefully between the "presidential communications privilege" and the "deliberative process privilege." In that case, the court dealt only with the presidential communication privilege but observed that both the communications privilege and the deliberative privilege are executive privileges designed to protect the confidentiality of executive branch decision-making. It's the deliberative process privilege that Obama invoked in the current dispute over Operation Fast and Furious.

President George W. Bush invoked executive privilege for the first time in his administration to block a congressional committee trying to review documents about a decades-long scandal involving FBI misuse of mob informants in Boston.

Associated Press writer Pete Yost contributed to this story.