As a candidate, Barack Obama once endorsed a ban on handguns and favored restrictions on the purchase and possession of firearms. So when gun owners heard of Operation Fast and Furious, many feared the worst.

Now, newly revealed emails suggest that if the gun-running operation didn't start out with that intent, as administration officials insist, the program certainly led to discussions on new gun regulations.

"There's a lot of talk that President Obama stated that he is working for gun control with alternative methods," said Arizona gun dealer Jeff Serdy. "I hope this isn't one of them."

Serdy and others suspect the Obama administration used the gun-running operation to support regulations Congress would not even consider, namely, a rule requiring gun stores in the Southwest to report anyone who tries to buy multiple "long guns," or rifles, in a one-week period.

"If the American people learn that the motivations for all of this was to make a case to deprive them of their Second Amendment rights or to make a case to further the (Justice) department's ability to further regulate gun rights within the United States, that would make them very angry," said Arizona Republican Rep. Trent Franks.

Holder insists that's not accurate.

"Clearly, an attempt to use Fast and Furious as a way to bolster the request for that long-gun regulation would have been foolhardy," he told the House Judiciary Committee last week.

There is no evidence the administration initially considered using the operation to justify stronger gun laws. But as the investigation dragged on, and Washington saw more and more weapons from U.S. gun stores show up at Mexican crime scenes, at least some officials saw a political argument developing to support their legislative agenda.

In March 2010, Holder's Chief of Staff Gary Grindler attended a detailed briefing on Fast and Furious in Washington. In handwritten notes, Grindler wrote the words "long rifle," "multiple sale" and "need regulation" in the margin of a briefing paper.

On July 14, 2010, Bureau of Alcohol, Tobacco, Firearms and Explosives Assistant Director Mark Chait asked then-ATF Phoenix Special Agent in Charge Bill Newell "if these guns were all purchased from the same (licensed gun dealer) and at one time. We are looking at anecdotal cases to support a demand letter on long-gun multiple sales."

On Jan. 4, 2011, Newell apparently saw the opportunity to publicly push for the new gun regulation. The Fast and Furious news conference provides "another time to address multiple sale on long guns issue," he wrote Chait.

A day after that news conference, Chait replied in an email: "Bill -- well done yesterday ... in light of our request for demand letter 3, this case could be a strong supporting factor if we can determine how many multiple sales of long guns occurred during the course of this case."

The "demand letter" would require border-state gun stores to report buyers who try to purchase multiple rifles or long guns in a one-week period.

Two months earlier, U.S. Attorney Dennis Burke had an email exchange with his counterpart in Washington state, Jenny Durkan. Burke informed her of the Fast and Furious case and its use of straw buyers to deliver guns to Mexico that "have been directly traced to murders of elected officials in Mexico City by the cartels."

Durkan wrote back: "Let me know when you have time to talk. I want to discuss our approach in enforcing gun sale laws at (gun stores) and gun shows."

Many gun owners add up the memos and see motivation -- a backdoor attempt by the Obama administration to justify limits on guns that a Republican-controlled Congress would not consider.

"I'm talking after the fact," Rep. Dan Lungren, R-Calif. told Holder last week. "When you screw up, you ought to say you screwed up and then don't allow your screw-up to be the basis for trying to extend your legislative agenda."

"The federal government certainly aided and abetted gun trafficking, which then may very well have been the proximate cause of a border agent's death," Rep. Trey Gowdy, R-S.C., said, referencing the death of Border Patrol agent Brian Terry.

"I will let the civil experts sort out civil liability. There is plenty of moral culpability to go around," Gowdy said.

Many Democrats see the issue differently -- if agents knew people were repeatedly paying cash for assault rifles, they'd be easier to track and catch, thereby slowing the "iron river of guns" the administration claims flow uninterrupted from U.S. gun stores to Mexican cartels.

Therefore, Fast and Furious demonstrates a need for new gun controls.

"When the administration and ATF say they want multiple long gun sales reported, it's so we can identify these straw purchasers, so we can go after them and prevent the flow of these guns into Mexico," said Rep. Adam Schiff, D-Calif.

The attorney general also criticized Congress for opposing this long gun registry.

"Earlier this year, the House of Representatives actually voted to keep law enforcement in the dark when individuals purchase semi-automatic rifles and shotguns in Southwest border gun shops," Holder said. "Providing law enforcement with the tools to detect and to disrupt illegal gun trafficking is entirely consistent with the constitutional rights of law-abiding citizens."

But Republicans take issue with that point.

Law enforcement was not 'in the dark' when individuals purchased Fast and Furious weapons, they say. Rather, ATF agents received real-time -- and sometimes advanced -- notice from cooperating gun dealers when suspected straw buyers purchased weapons. Buyers frequently called in their order before showing up. Gun store owners would give the straw buyers a pick-up time specifically to give ATF agents plenty of time to set up their cameras and surveillance teams.

In one email, Burke called the gun stores 'evil' and ATF brass in Washington also cooperated for a story in The Washington Post in December 2009 suggesting border-state gun stores were responsible for Mexico's cartel violence.

Internally, ATF officials admit cooperating gun stores like Lone Wolf in Phoenix -- singled out in the Post story -- actually helped the operation, dutifully faxing the names, addresses and serial numbers of the guns that the straws bought, often the same day. Lone Wolf also allowed the ATF to install cameras inside the store, giving ATF officials coast to coast real-time information about purchases and purchasers.

Holder's critics say he is setting their argument for them. According to the facts in the case, 93 multiple handgun purchases were made by Fast and Furious suspects, averaging nearly five handguns per purchase. These were already required to be reported under existing regulations.

Those same suspects also purchased 148 multiple long-gun purchases, averaging over 9 long guns per purchase. ATF had hundreds of reasons to arrest these buyers, but chose not to, they claim.

The administration argue that guns purchased at mom-and-pop gun shops in the border states are largely responsible for drug cartel violence in Mexico. Gun control advocates on Capitol Hill, like Senator Diane Feinstein, D-Calif., have repeatedly claimed 70 to 90 percent of the guns used in crimes in Mexico come from such stores.

"Of the nearly 94,000 (weapons) that have been recovered that have been traced in Mexico in recent years, over 64,000 of those guns were sourced to the United States of America; 64,000 of 94,000 guns sourced to this country," Holder told senators in November.

Republicans say Holder is playing games with the statistics. The definition of a "U.S.-sourced gun" is overly broad, they contend. It includes guns manufactured in the United States even if never sold by a federally licensed gun dealer in the United States.

Such weapons may have been legally exported to foreign governments, through direct military sales, which are sanctioned by the State Department. Those may be stolen or otherwise fall into the wrong hands. That cannot be properly blamed on Americans exercising their Second Amendment freedoms, argues Sen. Charles Grassley, R-Iowa, a leading congressional investigator of the Fast and Furious case.

According to ATF statistics, of the 21,313 guns submitted for tracing by the government of Mexico in 2009, 5,444 of them, or 25 percent, traced back to federally licensed gun dealers in the United States.

Similarly, in 2010, of 7,971 guns submitted for tracing by the government of Mexico, 2,945 -- 37 percent -- traced back to federally licensed gun dealers in the U.S.

"We in the gun industry knew from day one the allegations that the preponderance of sales came from gun stores like this one was totally not true," said Lynn Kartchner, owner of Allsafe Security, a gun shop in Douglas, Ariz.

In a Nov. 8, 2011, court filing, the chief of ATF's Firearms Operations Division made a declaration that "in 2008, of the approximately 30,000 firearms that the Mexican attorney general's office informed ATF that it had seized, only 7,200, or one quarter of those firearms, were submitted to ATF for tracing."

Based on these statistics, the total sample of guns submitted for tracing is not representative of all the guns found in Mexico.

Grassley and other Republicans say Democrats refuse to factor in perhaps the largest source of U.S. guns in Mexico: direct commercial sales to the government of Mexico approved by the U.S. State Department -- many of which are diverted to violent cartels.

In 2009, the State Department approved sales of 18,709 weapons to Mexico, almost 10 times the number sold to illegal straw buyers in Fast and Furious, and more guns than the U.S. sold to either Afghanistan or Iraq. That number includes $20 million in semi- and fully-automatic weapons.