In the wake of former president Donald Trump’s impeachment acquittal for inciting the deadly attack on the Capitol, House Speaker Nancy Pelosi said she would push for an investigation similar to the bipartisan commission that investigated the Sept. 11, 2001, terrorist attacks.

Lawmakers from both sides of the aisle agreed.

“We need a 9/11 Commission to find out what happened and make sure it never happens again‚” Sen. Lindsey O. Graham (R-S.C.), a longtime Trump ally, said this past weekend on “Fox News Sunday.”

Rep. Madeleine Dean (D-Pa.), a House impeachment manager, said, “There must be a full commission, an impartial commission, not guided by politics, but filled with people who would stand up to the courage of their conviction.”

But in their zeal to “investigate and report,” as Pelosi put it, on violence at the Capitol, lawmakers have placed the 9/11 Commission on a historical pedestal of patriotic transparency that doesn’t quite square with its past. The 585-page report submitted to Congress in 2004 was, according to historians and national security experts, an incomplete report marred by political warfare.

“Despite claims from all sides that what was needed was an unfiltered, non-partisan and accurate review of what went wrong and how it went wrong,” David Wallace, a University of Michigan government secrets scholar, wrote in 2011, “the archival record surrounding 9/11 was shaped as much by political concerns over blame and responsibility (and evading it) as it was by good faith efforts to get to the heart of the matter.”

Former New Jersey governor Thomas H. Kean (R) and former congressman Lee H. Hamilton (D-Ind.), the chair and vice chair, respectively, of the 9/11 Commission, laid out the repeated roadblocks they faced in their 2006 book “Without Precedent: The Inside Story of the 9/11 Commission.” The title of Chapter 1: “SET UP TO FAIL.”

“The chief obstacle,” Kean and Hamilton wrote, “was the White House.”

President George W. Bush, who was facing a reelection campaign in 2004, and other Republicans argued that a so-called Joint Inquiry underway in Congress was enough.

The White House said that “an independent investigation would distract the government from waging the ongoing war on terrorism,” the authors wrote. “At several points, it appeared that the proposal to create a 9/11 Commission was dead.”

But following pressure from the victims’ families, the White House caved, allowing the commission to go forward.

From the outset, neither side — Republicans nor Democrats — fully trusted the other. They wrangled over budgets, access to documents and other matters almost immediately. One of the most contentious early battles was over access to the Joint Inquiry report by Congress.

White House Counsel Alberto Gonzales, who referred to Bush as his “client,” was the chief gatekeeper in the White House. “Let me take this back to my client,” he would say, according to Kean and Hamilton. “I’ve got to protect my client.”

Throughout the investigation, access to key documents and testimony was denied.

“Challenges ranged from questionable classification to politically motivated declassification,” wrote Wallace, the government secrets scholar.

Bush and Vice President Richard B. Cheney, after initially balking at testifying, agreed to be interviewed together — a highly unusual way of questioning key witnesses in any investigation that was criticized for potentially allowing them to stay on the same page.

In the end, it was the CIA that proved most intractable.

Director George Tenet refused access to terrorist detainees. Two years after their book came out, Kean and Hamilton were startled by news reports that the CIA had destroyed videotaped interrogations of the detainees. They had not even known the videotapes existed.

Kean and Hamilton blasted the CIA in a New York Times op-ed in early 2008.

“A meeting on Jan. 21, 2004, with Mr. Tenet, the White House counsel, the secretary of defense and a representative from the Justice Department also resulted in the denial of commission access to the detainees,” Kean and Hamilton wrote. “Once again, videotapes were not mentioned.”

The CIA said it would pose some questions from the commission to the detainees and then report back.

“But the commission never felt that its earlier questions had been satisfactorily answered,” Kean and Hamilton wrote. “What we do know is that government officials decided not to inform a lawfully constituted body, created by Congress and the president, to investigate one the greatest tragedies to confront this country.”

Their conclusion: “We call that obstruction.”

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