For all the controversy that has plagued the U.S. Department of Justice under Attorney General Eric Holder Jr., from terror-trial venues to voting and immigrant rights issues, nothing has had more sticking power than the botched gun-trafficking probe called Operation Fast and Furious.

If Holder was hoping the flap over Fast and Furious would quietly subside, that hasn’t happened. And it isn’t likely. The congressional inquiry into the flawed program will continue into the new year and the Justice Department hasn’t wrapped up its internal investigation.

Fast and Furious, the operation in which federal agents allowed straw purchasers to buy firearms in the United States and transport them to Mexico, moved beyond the fringe and into the mainstream over the year.

Reporters questioned President Barack Obama about his confidence in Holder’s leadership. Holder shook up the top command of the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF). Dozens of Republican members of Congress called for Holder’s resignation and a senior Republican senator in Congress, Chuck Grassley of Iowa, demanded the termination of Assistant Attorney General Lanny Breuer, the Criminal Division’s top lawyer. For his part, Holder tried to remain silent about the controversial gun-trafficking probe as Republican leaders on Capitol Hill lashed federal prosecutors and Justice Department top brass. But he couldn’t stay out of the fray for long.

The attorney general went on the offensive in October, complaining about what he described as inflammatory rhetoric swirling around Fast and Furious. Holder charged that some critics were using Fast and Furious to score political points. “[E]ach of us has a duty to act, and to rise above partisan divisions and politically motivated ‘gotcha’ games,” Holder said at a House Judiciary hearing in December. “The American people deserve better. It is time for a new dialogue about these important issues — one that is respectful, responsible, and factual.”

All the while, Republican leaders on Capitol Hill pressed DOJ for more information about its handling of Fast and Furious. House Judiciary Chairman Lamar Smith (R-Texas) in October called on Obama to appoint a special counsel to determine whether Holder misled members of Congress about when he first learned about the operation. Rep. Darrell Issa, the chairman of the House Oversight Committee, earlier this month compared Holder to President Richard Nixon’s attorney general John Mitchell, convicted in the Watergate scandal.

The Justice Department has tried to focus the debate on the need for more law enforcement tools to staunch the flow of guns into Mexico, and Democrats on the Hill have sounded that refrain. If there’s one point both sides agree on, it’s this: The effects of the Fast and Furious operation will be felt for years as guns that should have been seized show up at crime scenes on both sides of the border.

What follows are key moments in the Fast and Furious controversy:

DEC. 14, 2010

U.S. Border Patrol agent Brian Terry was fatally shot in southern Arizona along the Mexico border. Investigators linked two firearms to the Fast and Furious investigation. At least one person has been indicted in connection to the murder.

JAN. 27, 2011

Grassley wrote to then-ATF acting dir­ector Kenneth Melson to inquire about “Project Gunrunner,” an overarching federal anti-gun trafficking program. “Members of the Judiciary Committee have received numerous allegations that the ATF sanctioned the sale of hundreds of assault weapons to suspected straw purchasers, who then allegedly transported these weapons throughout the southwestern border area and into Mexico,” Grassley wrote.

FEB. 4

Assistant Attorney General Ronald Weich, who leads the Department of Justice’s Office of Legislative Affairs, responded to Grassley in a letter that makes the claim that “ATF makes every effort to interdict weapons that have been purchased illegally and prevent their transportation to Mexico.” Weich’s letter became a centerpiece of Republican criticism that DOJ was not fully up-front with Congress.

MAY 3

Holder and Issa spar at a House Judic­iary hearing over when the attorney general first learned about Fast and Furious. “I’m not sure the exact date. But I probably heard about Fast and Furious for the first time over the last few weeks,” Holder said. He noted at one point that Fast and Furious “has gotten a great deal of publicity.” Issa saw an opening. “Yeah, there are dead Americans as a result of this failed and reckless program,” he said. Holder described as “offensive” Issa’s remark that DOJ is “basically guilty” of allowing weapons to kill Americans and Mexicans.

JUNE 15

Weich testified before the House Over­sight and Government Reform Commit­tee, addressing questions about the DOJ’s response to congressional demands for documents. House and Senate Repub­licans have accused DOJ of not providing sufficient responses to congressional inquiries. DOJ maintains it is fully cooperating with the congressional inquiry.

AUG. 30

Melson, the ATF acting director, packed up his office. Holder named Melson the senior adviser on forensic science for the DOJ Office of Legal Policy. The U.S. attorney in Minnesota, B. Todd Jones, a former partner at Robins, Kaplan, Miller & Ciresi, took over for Melson. Dennis Burke, the U.S. attorney for Arizona, resigned.

OCT. 7

In a letter to Congress, Holder said “the public discourse concerning these issues has become so base and so harmful to interests” that he felt compelled to speak more in depth than he had previously. “Much has been said about my congressional testimony earlier this year regarding Fast and Furious,” Holder wrote. “My testimony was truthful and accurate and I have been consistent on this point throughout. I have no recollection of knowing about Fast and Furious or of hearing its name prior to the public controversy about it.”

NOV. 1

Breuer battled Grassley at a Senate Judiciary subcommittee hearing. Breuer revealed he knew about the controversial gun-trafficking investigative techniques in April 2010 in an operation called “Wide Receiver.” But he didn’t connect it with Fast and Furious. “I regret that in April of 2010 that I did not draw the connection between Wide Receiver and Fast and Furious. Moreover, I regret that even earlier this year that I didn’t draw that connection,” Breuer told Grassley during one exchange. Grassley pressed Breuer why he didn’t tell top officials, including Holder, about the gun-walking tactics in Wide Receiver. Breuer said he “thought that dealing with the leadership of ATF was sufficient and reasonable.”

NOV. 8

Back on Capitol Hill, the attorney general quarreled with Republican members of the Senate Judiciary Committee, fending off the suggestion that DOJ officials intentionally misled Congress in the now-famous Feb. 4 letter from Weich. Holder acknowledged the letter contained inaccurate information, but he refused to call the material “false.” Holder said no DOJ official had any intent to deceive members of Congress.

DEC. 2

DOJ sent thousands more pages to Congress, explaining the generation of the Feb. 4 letter. Deputy Attorney General James Cole told Congress that DOJ has — in a rare move — retracted the letter because of its claim that ATF makes every effort to stop guns from flowing into Mexico. “As indicated in congressional testimony by senior department officials on several occasions, however, facts have come to light during the course of this investigation that indicate that the February 4 letter contains inaccuracies,” Cole wrote. Weich, according to Cole, relied on information provided by supervisors at ATF and in the U.S. Attorney’s Office for the District of Arizona.

DEC. 8

Republican members of the House Judiciary Committee criticize Holder and question why he hasn’t fired anyone. “Getting to the bottom of this is something we all want to do,” Holder told Rep. Jim Sensenbrenner (R-Wis.). Holder said “allowing guns to ‘walk’ — whether in this administration or the prior one — is wholly unacceptable. The use of this misguided tactic is inexcusable. And it must never happen again.” Issa asked Holder whether he would voluntarily show up for another hearing on Fast and Furious in the new year. Issa suggested he would issue a subpoena if the attorney general refuses to participate.

DEC. 14

Grassley issued a statement marking the one-year anniversary of Terry’s death. “We’ll get to the bottom of what led to that sad day one year ago when one of our own was killed because of an ill-advised gunwalking policy concocted by the federal government,” Grassley said. “The Terry family deserves no less than a full accounting of how this all happened sooner rather than later.”

Mike Scarcella can be contacted at mscarcella@alm.com.