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, which 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 "Fast and Furious" gun-tracking operation to advance a gun control agenda.

Hoyer would not give a number of potential defectors.

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 see "if they can slow him down," said the Rev. Al Sharpton.

Issa, in a letter to the president dated Monday and made public Tuesday, 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." Courts have routinely "affirmed the right of the executive branch to invoke the privilege even when White House documents are not involved," Schultz said.

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