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Democrats went on the offensive Thursday over the contempt proceedings against Attorney General Eric Holder, with the White House calling the campaign a "fishing expedition" and Nancy Pelosi accusing Republicans of targeting Holder because of his department's crackdown on state voter ID laws.

While Republicans opened the door to potentially averting a full House contempt vote next week, Democrats indicated Thursday they were ready to fight rather than turn over the disputed documents Republicans are seeking for their probe into Operation Fast and Furious.

"This has become a political fishing expedition," White House Press Secretary Jay Carney said Thursday.

Pelosi, in a press briefing earlier in the day, said the anti-Holder push is part of a scheme to "suppress" the vote.

"They are going after Eric Holder because he is trying to overturn voter suppression in the states. This is a plan," Pelosi said.

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Asked about Pelosi's claim, Carney said he could not "divine" Republicans' motivation for pursuing the contempt case against Holder. But he adamantly defended both Holder and President Obama for his decision to assert executive privilege over the documents Republicans are seeking.

"Those kinds of deliberations have been protected under privilege as a matter of the separation of powers ... dating back 30 years," Carney said, describing the documents in question as "internal Executive Branch documents."

Republicans, who voted at the committee level in favor of contempt Wednesday, are seeking more than 70,000 additional documents to answer questions on Fast and Furious. They bristled at Obama's eleventh-hour privilege claim -- and also suggested that the White House was acknowledging involvement in Fast and Furious discussions by asserting privilege over the documents.

House Speaker John Boehner went further Thursday, saying: "The decision to invoke executive privilege is an admission that White House officials were involved in decisions that misled the Congress and have covered up the truth."

He asked, "What is the Obama administration hiding in Fast and Furious?"

Meanwhile, Sen. Marco Rubio, R-Fla., added his name Thursday to list of lawmakers calling for Holder's resignation.

The White House and Justice Department, though, downplayed the potential implications of the executive privilege claim.

Justice Department officials noted that the privilege assertion does not have to pertain to communications involving the president or White House staff. Any "deliberative communications" among officials in the Executive Branch, they said, could be covered.

In other words, they argued that just because Obama is locking down the documents doesn't mean he had anything to do with the Fast and Furious discussions.

Executive privilege has been invoked 24 times since the presidency of Ronald Reagan. This was Obama's first time asserting it.