4.00pm: The House of Representatives is preparing to vote on a resolution to hold the attorney general, Eric Holder, in contempt of Congress for refusing to hand over justice department documents pertaining to the so-called Fast and Furious scandal. We're going to live blog the vote. Here's a summary of where things stand:

• A House vote of contempt could do grave damage to relations between the White House and Republican leaders on the Hill. Negotiations between the two sides to try to prevent the disagreement from playing out on the House floor broke down Wednesday morning.

• House Republicans led by Rep Darrel Issa of California, chairman of the House Oversight Committee, accuse Holder of concealing documents laying out the extent of a secret federal operation to crack gun smuggling operations across the Mexico border. President Obama has invoked executive privilege to avoid releasing certain documents. It is the first time he has done so in response to a federal inquiry.

• In the most prominent initiative, known as Operation Fast and Furious, agents allowed illegal gun sales to proceed in an effort to track buyers to larger criminal rings. A gun sold in one such operation has been tied to the killing of a federal agent, Brian Terry, in December 2010.

• The Justice Department argues that it has fully complied with the congressional investigation into Operation Fast and Furious, including turning over emails between Holder and subordinates and internal documents relating to the program. Republican members of Congress accuse the DoJ of hiding something – in part because the department's first response to a Congressional query on the matter was an official letter stating, falsely, that the gun-walking program never existed. Holder subsequently opened an internal investigation.

• The hearings are being broadcast live on C-SPAN.

4.40pm: The House has voted to find the attorney general in contempt of Congress. 255-67, with one member voting present.

17 Democrats crossed the aisle to vote in favor of the contempt resolution, while two Republicans voted against.

The first contempt resolution pertained to criminal contempt, which means the case will be referred to criminal court. Now the House is considering a civil contempt measure.

4.50pm: House minority leader Nancy Pelosi and Rep. John Lewis led a walkout of Democratic lawmakers during the contempt vote.

Pelosi has posted a photo of the walkout to her Facebook page.

Democratic members with press after they #walkout of the AG Holder contempt vote twitter.com/OfficialCBC/st… — The CBC (@OfficialCBC) June 28, 2012

5.03pm: Attorney General Holder is speaking on the vote finding him in contempt of Congress.

"The outcome is unnecesary and unwarranted," he says. Holder says he has remained focused on "the priority of protecting the American people."

He say that when Operation Fast and Furious first came to light he took action. The program, he notes, "began in a previous administration" – that would be the administration of George W. Bush. "I made sure that it ended in this one," Holder says. "I also made sure that ... such tactics may never be used again."

Holder then accuses Congress of mounting an act of political theater.

"I had hoped that Congressional leaders would be good-faith partners in this work," he say. "And some were. Others, however, have devoted their time and energy to [creating political theater] and truly absurd – truly absurd – conspiracy theories."

Holder says the same legislators who are conducting a public besmirchment of the DoJ "were nowhere to be found when it came time to look for solutions to the violence on both sides of the southwest border."

Congress finds time to attack the White House but not to address "a real and significant public safety threat," Holder says.

"Today's vote might make for good political theater in the minds of some, but it is at base a crass effort... the American people expect and deserve more."

"Ultimately their goal was the vote that, with the help of special interests, they now have engineered."

Holder says the vote won't distract him from the work at hand. "I'm going to get back to it. I'd suggest that those who engineered today's vote do the same."

5.09pm: Andrea Stone at the Huffington Post describes the incident that set in motion the process that came to a head in Washington today: the killing of US border patrol agent Brian Terry:

A few minutes after 11 p.m., near the town of Rio Rico, the squad spotted five men they suspected were illegal immigrants. Details of what happened next remain sketchy. According to a report released by congressional Republicans, at least two of the suspects were carrying rifles. The officers reportedly identified themselves as federal agents, but the men refused to drop their weapons and one of them opened fire. A ferocious gun battle ensued. Terry was shot once. He died en route to the hospital. He was 40 years old and had been a Border Patrol agent for less than four years.

5.16pm: The White House has released a statement calling the House vote "a tranparently political stunt."

Here's the statement (h/t: Politico):

At the beginning of this year, Republicans announced one of their top priorities was to investigate the Administration and to ensure that President Obama was a one-term President. Despite the major economic challenges facing the country, they talked openly about devoting taxpayer-funded, Congressional oversight resources to political purposes. The problem of gunwalking was a field-driven tactic that dated back to the George W. Bush Administration, and it was this Administration's Attorney General who ended it. Attorney General Holder has said repeatedly that fighting criminal activity along the Southwest Border – including the illegal trafficking of guns to Mexico has been is a top priority of the Department. Eric Holder has been an excellent Attorney General and just yesterday the Chairman of the House Oversight Committee acknowledged that he had no evidence – or even the suspicion – that the Attorney General knew of the misguided tactics used in this operation. Yet, Republicans pushed for political theater rather than legitimate Congressional oversight. Over the past fourteen months, the Justice Department accommodated Congressional investigators, producing 7,600 pages of documents, and testifying at eleven Congressional hearings. In an act of good faith, this week the Administration made an additional offer which would have resulted in the Committee getting unprecedented access to documents dispelling any notion of an intent to mislead. But unfortunately, a politically-motivated agenda prevailed and instead of engaging with the President in efforts to create jobs and grow the economy, today we saw the House of Representatives perform a transparently political stunt.

Feel the bipartisan love.

5.25pm: It's the first time a sitting Cabinet member has been held in contempt of Congress.

Attorney General Holder argued that his role has been to shed light on the Fast and Furious operation and not to obscure it. It was a Bush program, he points out. Now the Associate Press has published emails revealing Holder's attempt to root out details of the program:

On Feb. 23, aides passed along to the attorney general the CBS story alleging gun-walking, and the attorney general shot back, "We need answers on this. Not defensive BS. Real answers." Five days later, Holder asked the Justice Department's inspector general to investigate. On March 3, Cole, the No. 2 official at the Justice Department, emailed his staff: "We obviously need to get to the bottom of this." Holder was skeptical of any assurances. "I hope the AG understands that we did not allow guns to walk," an official at the ATF's Washington headquarters said on March 10 in an email that Holder's aides forwarded to the attorney general. In a response, Holder wrote, "Do they really, really know" that there was no gun-walking?

5.38pm: Congress now has found Eric Holder in civil contempt of Congress by a vote of 258-95, with 5 voting present.

The vote follows an earlier resolution finding the attorney general in criminal contempt.

Practically speaking, it is unlikely the attorney general will face repercussions of the contempt findings beyond going down as the first sitting Cabinet member ever to be found in contempt of Congress.

As to the potentially political nature of these votes: there's no evidence, but certain data could suggest that the contempt vote against Eric Holder may have been politically motivated. A whopping total of 19 lawmakers, 4%, crossed party lines in the vote.

Only two Republicans voted against their party. We hereby single them out for public ridicule – or praise, depending on your perspective. They are:

Rep. Steve LaTourette, R-Ohio

Rep. Scott Rigell, R-Va

5.39pm: The House is now speeding through a series of bills renaming post offices.

6.00pm: We're going to wrap up our live blog coverage of the House of Representatives holding Attorney General Eric Holder in contempt of Congress. Here's a summary of the latest developments:

• The House found Holder in both criminal and civil contempt of Congress. He became the first sitting Cabinet member to be found in contempt. The vote broke along partisan lines. Many Democrats staged a walkout to protest the vote.

• Holder delivered a statement accusing House Republicans of staging political theater. "I had hoped that Congressional leaders would be good-faith partners in this work," he said. "And some were. Others, however, have devoted their time and energy to [creating political theater] and truly absurd – truly absurd – conspiracy theories."

• The White House released a statement accusing House Republicans of staging political theater. "But unfortunately, a politically-motivated agenda prevailed and instead of engaging with the President in efforts to create jobs and grow the economy, today we saw the House of Representatives perform a transparently political stunt," the White House said.

• Rep. Darrel Issa, R-Calif., chairman of the House oversight committee, claimed a victory for the family of border patrol agent Brian Terry, who was shot dead with an automatic rifle the government had lost track of in the Fast and Furious program. Terry's family members supported the resolution.

Rep. Steve LaTourette, R-Ohio, was one of two Republicans to cross party lines to vote against the contempt resolution. A statement he made after the vote was reported by Jonathan Weisman of the New York Times: