Operation Fast and Furious became a source of public outrage when it was revealed that federal investigators let 2,000 guns go from Arizona to criminal groups in Mexico.
But now it has also become a source of political gamesmanship, with politicians raising campaign cash by talking about Fast and Furious, denying all the while that their interest is political.
To sort reality from rhetoric, the Star analyzes key facts and claims surrounding the investigation. Here's a rundown of what we know about the controversial guns investigation and key claims made about it:
Fast and Furious so far
The operation began in 2009, when a group of ATF agents formed in Phoenix to monitor people buying weapons there and sending them to criminal organizations in Mexico.
It wasn't a new concept: A broader U.S. initiative called Project Gunrunner began in 2005, aiming to slow the flow of weapons from the United States to Mexico.
In 2006, ATF agents in Tucson began an operation called Wide Receiver, in which a Tucson firearms dealer sold hundreds of weapons to people who were buying guns for criminal groups in Mexico. The dealer, Mike Detty, said he was initially told Mexican authorities were involved in the operation, but later it became clear they weren't.
A similar operation happened in Phoenix in 2007, but ATF agents told Mexican authorities about it.
As Operation Fast and Furious progressed, some ATF agents involved protested against letting so many guns "walk" - that is, leave the custody and surveillance of investigators. But supervisors said the plan had approval from above.
The operation and its tactic of letting guns into Mexico came to light only after Dec. 15, 2010, when Border Patrol Agent Brian Terry was shot to death near Rio Rico.
FBI agents recovered two weapons at the scene, and ATF agents determined they had been sold as part of the Fast and Furious investigation. But it took more than two months before officials acknowledged how those weapons arrived there. And then, it was only under pressure from U.S. Sen. Charles Grassley, who had been tipped off by ATF agents.
Muted response from Mexico
Operation Fast and Furious took place amid an explosion of demand for weapons from Mexico.
President Felipe Calderón had launched an attack on Mexico's drug traffickers after taking office in 2006, and by the time President Obama was elected, battles were raging among mafias and between the criminals and government forces.
"As that conflict mounts and there's greater competition, they're looking for greater firepower," said Eric L. Olson, senior associate at the Woodrow Wilson Center's Mexico Institute in Washington D.C.
Seizures of firearms by Mexico's military in drug-trafficking operations rose from 4,948 weapons in 2006 to 28,128 in 2010. But even that was just a fraction of the criminals' arsenals.
As a result, even before Obama took office on Jan. 12, 2009, Mexico's president met with Obama and asked him to slow the flow of guns and money southward across the border.
Still, when it emerged this year that Bureau of Alcohol Tobacco Firearms and Explosives agents had facilitated the sale of 2,000 weapons to Mexican criminal groups, Calderón's reaction was muted.
In an interview with The New York Times, published Oct. 15, Calderón declined to lash out at the Obama administration or the ATF. This showed a maturation of the binational relationship, said David Shirk, director of the Trans-Border Institute at the University of San Diego.
"If this had happened 20 years ago, or even 15 years ago, this would have caused enormous scandal and outrage in Mexico," Shirk said. "At this point we are so intertwined and intermeshed … in coordinating law enforcement efforts that it would be difficult to pull the plug on that as a result of one incident."
Still, the weapons are being used in crimes in Mexico. In July, the acting ATF attaché Carlos Canino in Mexico testified that Fast and Furious weapons have been recovered at 200 crime scenes in Mexico. A Mexican congressman, Humberto Benitez Treviño, told the Los Angeles Times he was told in March that 150 people had been killed or wounded with Fast and Furious weapons, and he estimated that number had doubled by September.
The scent of cover-up
Word of an ATF investigation and its possible link to Terry's death began to leak in January, as Grassley received reports from ATF agents.
On Jan. 25, the ATF special agent in charge of the Phoenix office, Bill Newell, was asked at a press conference if guns were allowed into Mexico as part of Operation Fast and Furious. His response: "Hell, no."
The appearance of obfuscation has cloaked Fast and Furious ever since. U.S. Rep. Darrell Issa, chairman of the House Oversight and Government Reform Committee, revealed Oct. 6 that U.S. Attorney General Eric Holder had been briefed on the investigation months before Holder said he learned of it.
As early as July 2010, Holder was told in written briefings that 1,500 guns had been provided to the Sinaloa cartel under Fast and Furious, but testifying on May 3 Holder said he'd first heard of the operation in the "last few weeks."
As a result, some Republican politicians have begun comparing Fast and Furious to Watergate. Pinal County Sheriff Paul Babeu, who has been hammering on the issue in public appearances since May, told a Tucson Tea Party audience last month: "This scandal that we're talking about tonight, Fast and Furious, will literally dwarf anything in our life that we've seen."
In an email, Babeu explained: "If you knew that a foreign power had caused over 2,000 guns to arrive in the hands of America's most dangerous criminals, what would you say? What if those weapons had been used to commit more than 200 murders? Now consider that the federal government did just that - and to an ally. Nobody died because of Watergate and no treaties were violated."
Resignations have resulted from Fast and Furious: U.S. Attorney for Arizona Dennis Burke and acting ATF director Kenneth Melson both resigned in the wake of the investigation
Still, political experts say no evidence has emerged that the White House conceived or directed Operation Fast and Furious, let alone had a motive for it.
"To put this in the same category (as Watergate) is just preposterous," said Stanley Kutler, an emeritus professor at the University of Wisconsin who wrote "The Wars of Watergate", a history of the era. "What happened down there is a terrible thing, and it's terrible in its own right, but it's apples and oranges."
Watergate was much more than a 1972 burglary at Democratic headquarters in Washington, D.C., Kutler noted: "Watergate was the most significant constitutional crisis in the United States since the Civil War."
A gun-control conspiracy?
What's missing in the Watergate comparison is a clear motive for the Obama White House to send weapons to Mexico. The National Rifle Association and its allies have filled that void with a theory that, in Babeu's words, Fast and Furious was part of a "master plan" to bring about more gun control.
Their version goes like this:
1. Obama and Holder support gun control but needed a pretext to implement it.
2. The administration argued falsely in 2009 that U.S. guns made up 90 percent of those used in Mexican gun crimes. That was the same time when Operation Fast and Furious began.
3. By flooding Mexico with high-powered weapons they were able to justify restrictions on U.S. guns. In fact, in July 2011, the administration put in place a rule requiring border-state firearms dealers to report anyone who buys more than one assault-type rifle within a five-day period.
"Lo and behold, Mr. President, while you were making the case to restrict our constitutional right to bear arms, it was you and your government that was facilitating these arms that have helped to destabilize Mexico," Babeu told the Tucson Tea Party event.
However, there is little or no evidence to support this argument.
Author Robert Spitzer called the theory "nonsense." Spitzer, a longtime NRA critic who wrote "The Politics of Gun Control," said NRA "has been virulently anti-ATF for 30 years."
He said the NRA has worked Congress to limit ATF's budget and powers, but complains when the agency can't do its job.
Even Calderón said in the October interview with The New York Times he didn't want to criticize Obama over Fast and Furious because it would hurt ATF and "strengthen the firearms industry."
Paul Charlton, the former U.S. attorney for Arizona who is now representing Terry's parents, said they are unconvinced.
"The family hasn't alleged a cover-up, but they are certainly following the investigation," he said, before pointing the finger toward Newell. "The one constant seems to be the ATF SAC (special agent in charge)."
'ACCESSORIES TO MURDER'
The NRA, Babeu and U.S. Rep. Paul Gosar, a Flagstaff Republican, have pushed their argument further in recent weeks, labeling federal employees involved in Fast and Furious possible "accessories to murder."
Said NRA executive Wayne La Pierre: "If any American citizen had intentionally provided the Mexican drug cartels with guns, and those Mexican drug cartels go out and kill people and commit hundreds of crimes, there isn't a United States attorney worth his salt that wouldn't indict that person for accessory to murder."
It was a step up in the rhetorical battle over Fast and Furious, and Gosar's similar comment finally drew out Holder, who had been cagey until then.
"Such irresponsible and inflammatory rhetoric must be repudiated in the strongest possible terms," Holder wrote Oct. 7 in a letter to six members of Congress. "Those who serve in the ranks of law enforcement are our nation's heroes and deserve our nation's thanks, not the disrespect that is being heaped on them by those who seek political advantage."
Two Republican former prosecutors from the Phoenix area agreed with Holder that the idea of prosecuting those involved in Operation Fast and Furious is going too far.
"I think that puts an impossible burden on law enforcement, to hold out that kind of talk," said A. Melvin McDonald, U.S. attorney for Arizona from 1981 to 1985. "To take what everybody believes is a colossal screw-up to the next level and consider it a crime is misguided."
Former Maricopa County Attorney Rick Romley called the idea of prosecuting people involved in Fast and Furious "crazy."
As a sheriff, he said, "Babeu should know better than that."
If prosecutions occurred in a case like this, the threat of criminal charges would prevent law-enforcement agencies from carrying out any risky operations in the future, Romley said.
Charlton said Terry's parents don't support charges either.
Fast, furious fundraising
The politics surrounding Operation Fast and Furious have grown to such an extent that candidates are raising money off the issue.
Babeu, who is exploring a run for Congress, promised to talk about Fast and Furious in an online invitation to a $100-per-person Paradise Valley fundraiser this month. He also advertised on the Drudge Report, asking readers to sign an online petition to "expose the truth about Operation Fast and Furious." A click took readers to Babeu's re-election page, where a prominent donation box accompanied the online petition.
Scottsdale public-relations executive Jason Rose, a supporter of the sheriff, noted the ad on Twitter: "Raising money fast and furious? Pinal county sheriff paul babeu citing u.s.-mexican gun scandal in drudge report ads." In an interview, Rose called the ads "aggressive, creative and interesting."
Asked via email about this use of Fast and Furious in fundraising, Babeu did not address the issue directly: "As an elected official, citizens are my bosses and I will continue to answer their demands for accountability and justice regarding this botched operation, which has put dangerous weapons directly into the hands of the Mexican drug cartels."
The politics of Fast and Furious are poised to get even hotter.
On Oct. 12, Issa subpoenaed Holder to testify at a hearing, now scheduled for Dec. 8. Issa plans to press Holder on those old Watergate questions: what he knew and when he knew it.
In a statement, Issa said: "Top Justice Department officials, including Attorney General Holder, know more about Operation Fast and Furious than they have publicly acknowledged."
On Friday, the ranking Democrat on the committee, U.S. Rep. Elijah Cummings, demanded that former acting ATF director Melson and former deputy director William Hoover also appear at the hearing. In a letter to Issa, he said Melson and Hoover would bolster the Democrats' version of how Fast and Furious came about.
"Both officials (have) also stated that they had not been aware of the controversial tactics being used in Operation Fast and Furious, had not authorized those tactics, and had not informed anyone at the Department of Justice headquarters about them. They stated that Operation Fast and Furious originated within the Phoenix Field Division, and that ATF headquarters failed to properly supervise it."
Said Fred Solop, a Northern Arizona University political science professor: "This is the type of issue that captures attention and has the potential to move people as we enter the election season."
Contact reporter Tim Steller at 807-8427 or firstname.lastname@example.org