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Republican lawmakers hounding the Obama administration for months over unanswered questions on the Benghazi attack will have their moment, on Wednesday, to demonstrate whether the internal response amounted to a cover-up -- as whistle-blowers give long-awaited testimony expected to challenge the White House's version of events.

Two of the whistle-blowers' opening statements were obtained by Fox News, and in the statements they defend their credibility in testifying about what happened last Sept. 11 in Libya.

"I am a career public servant," Greg Hicks' statement reads. "Until the aftermath of Benghazi, I loved every day of my job." He was deputy chief of mission in Libya and became top U.S. diplomat in the country after Ambassador Chris Stevens was killed in the terror attack.

The other statement, by Mark Thompson of the State Department Counterterrorism Bureau, is mostly biographical. Testimony also is due Wednesday from Eric Nordstrom, a diplomatic security officer who was formerly the regional security officer in Libya.

The administration has parried Republican allegations lately by arguing that the attack is old news, that the State Department already has investigated it and that Republicans are engaged in a political witch hunt.

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    But a series of carefully timed leaks on the whistle-blowers' testimony indicates House Republicans could have the goods to at least merit a second look at the administration narrative.

    "The question is, where's the accountability for lying to the American people?" Rep. Darrell Issa, R-Calif., chairman of the House Oversight and Government Reform Committee, told Fox News. "The American people were lied to."

    Issa claimed one "cover-up" is "undeniable" -- that the State Department botched security in Benghazi in the run-up to the attack. But, he said, "it still doesn't explain the president misleading the American people over a period of weeks."

    Three whistle-blowers are set to testify shortly before noon to the oversight committee Issa chairs.

    Issa's Democratic counterpart on the committee, Maryland Rep. Elijah Cummings, voiced skepticism about the leaks of the witnesses' claims in advance of the hearing.

    "If there was any matter that cries out for bipartisanship, it's this," he told Fox News, while raising criticisms that information about some witnesses wasn't available in advance to Democrats. "This is about making sure that our diplomatic core are safe. ... I want to go wherever the evidence leads, but I want all the evidence."

    Rep. Jason Chaffetz, R-Utah, a member of that committee, said if it weren't for lawmakers' persistence, "we would be left with a whole host of lies coming out of this administration, because they were not truthful about this."

    The "truth" surrounding the Benghazi attack has been elusive. The Obama administration has adamantly denied several of the latest charges, including a claim that then-Secretary of State Hillary Clinton and a key aide tried to cut the department's own counterterrorism bureau out of the chain of reporting and decision-making on Sept. 11. The administration also denied that the whistle-blowers in question were intimidated -- while behind the scenes questioning the credibility of the witnesses.

    The witnesses are expected to cover a breadth of material in their testimony Wednesday. Lawmakers have questioned to what extent security requests were ignored before the attack, whether the military could have done more to respond the night of the attack and whether talking points were intentionally changed for political reasons after the attack to downplay terrorism. The witnesses could address all three areas on Wednesday.

    A key area of interest is how the attack was described in the immediate aftermath.

    The Weekly Standard reported last week that the initial CIA talking points on the attack said "Islamic extremists with ties to al Qaeda participated in the attack." The reference to Al Qaeda was later taken out, and the initial reference to "attacks" was reportedly changed to "demonstrations."

    According to The Weekly Standard, State Department spokeswoman Victoria Nuland raised "serious concerns" at the time about the draft, concerned it could fuel criticism of the department.

    The language continued to be watered down.

    Issa told Fox News, in reference to the revisions, that "it's very clear ... that this was a political change."

    State Department officials released a statement Tuesday night labeled "Benghazi Attack Fack Check" to defend its security efforts.

    "No one is more determined than the State Department family to bring those who perpetrated this attack to justice and do everything we need to do to keep our people safe," the statement reads. "That's where our attention is, and we hope Congress and the media, too, can keep the focus."

    Hicks, according to a transcript, also told congressional investigators that he thought it "was a terrorist attack from the get go."

    The whistle-blowers will be able to provide a new perspective on what was happening on the ground that night.

    Hicks, according to transcripts, told investigators that the U.S. military could have prevented one wave of the deadly attack on American personnel in Benghazi if fighter jets had been promptly deployed. Further, he claimed that a second rescue team that was supposed to go from Tripoli to Benghazi early the next morning was told not to go.

    He said Special Forces personnel were planning to board a C-130 flight at around 6 a.m. local time on Sept. 12 but got a phone call when they were on their way to the flight telling them "you can't go now, you don't have authority to go now. And so they missed the flight."

    He added: "They were told not to board the flight, so they missed it," apparently because they did not have the "right authority."

    Thompson has also claimed that Clinton and a key aide effectively tried to cut the department's own counterterrorism bureau out of the loop that night.

    White House Press Secretary Jay Carney denied the claim on Monday.

    Daniel Benjamin, who ran the department's Counterterrorism Bureau at the time, also put out a statement Monday morning strongly denying the charges.

    "I ran the bureau then, and I can say now with certainty, as the former Coordinator for Counterterrorism, that this charge is simply untrue," he said. "Though I was out of the country on official travel at the time of the attack, I was in frequent contact with the Department. At no time did I feel that the Bureau was in any way being left out of deliberations that it should have been part of."