(CNSNews.com) - "The dam's about to break on Benghazi," Sen. Lindsey Graham (R-S.C.) told Fox News's Greta Van Susteren on Monday night. He said this week's testimony from State Department whistleblowers is "going to make you mad." He's also urging other witnesses to come forward.
Graham was among the first Republicans to speak to Greg Hicks, the number two diplomat in Libya when Benghazi was attacked.
Hicks will tell the House Oversight and Government Affairs Committee on Wednesday that everyone in Libya knew it was a terror attack from the very beginning, even though the Obama White House -- two months before the presidential election -- kept blaming a spontaneous protest arising from an obscure anti-Muslim video.
Graham told Fox News's Greta Van Susteren on Monday that Hicks is a "professional diplomat" who "doesn't want to get involved in politics." But he's also a "man of conscience" and the last person to speak to Ambassador Chris Stevens, who was one of the four Americans killed in the terror attack on Benghazi.
"He knows it was a terrorist attack from day one," Graham told Van Susteren. "And what baffles everybody that lived through this is how Washington could tell a story about what they lived through so different than what actually happened on the ground.
"And there's no other explanation, other than the people in Washington telling the story had political motivations, because the people on the ground are telling us what they lived through is completely different than what the president told the people about."
Graham said he's been asking for other Benghazi survivors to come forward, but "everybody feels chilled." The senator said "every agency in the government is stonewalling."
"The five people who were diplomatic security (in Benghazi) have never been talked to by the Congress. It's our job to oversee and provide oversight to the executive branch," Graham said. Congressional investigators will protect the identities of those diplomatic security personnel, but it's important to hear what they have to say. "We want to know what happened," he said.
Asked about State Department efforts to discredit Hicks by saying he has an axe to grind, Graham said as far as he's concerned "the only axe to grind...is that you can't let your government lie to you. You have four Americans dead, and the stories told by the highest levels of our government about how they died was a bunch of garbage."
Graham said that "frustrated" CIA agents, at least one of whom was on the ground in Benghazi the night of the attack, also are reaching out to congressional investigators. "The CIA generally got this right, and they feel frustrated about what happened that night, before and after. So we'll see where this goes," Graham said.
Graham previously has described multiple failings in Benghazi on the part of the Obama administration: Before the attack, repeated requests for tighter security were ignored by the State Department; during the 7-plus hours of the attack, "Americans in the field were abandoned," he said. And after the attack, the Obama administration provided misleading information to the American people.
"What we're finding out is that the story told by the State Department, Susan Rice, the president himself was so completely wrong and false," Graham told Van Susteren on Monday. "There's a reason. Why did Susan Rice and the president push this narrative that it was a spontaneous event caused by a hateful video? Because if the truth had come out seven weeks before an election (that) this was an al-Qaeda-inspired, pre-planned attack, it would undercut the narrative politically that bin Laden's dead, we're all safer.
"Political manipulation is rampant here. It is no accident that the story told by the Washington folks, including the president, was beneficial to the president and disconnected from reality, because we can't talk to anybody who actually lived through it. Now you got a guy coming forward called Greg Hicks..."