WASHINGTON — Five months after President Barack Obama called on lawmakers to approve his choice to lead the Bureau of Alcohol, Tobacco, Firearms and Explosives, the Senate is considering the nomination.

When B. Todd Jones appears before the Senate Judiciary Committee on Tuesday he will be just the second ATF nominee to face congressional questioning since the Senate was given authority to approve the agency’s chief in 2006. Like his predecessors, Jones’ nomination is likely a longshot, despite vocal support from law enforcement and the White House. The bureau hasn’t had a confirmed director for six years.

Jones is likely to face aggressive questioning from Republicans about his decisions as the top federal prosecutor in Minnesota and the ATF’s widely criticized gun-smuggling sting operation called “Fast and Furious.”

The White House again Monday urged the Senate to approve him.

“Todd Jones is a highly qualified nominee who has decades of experience in law enforcement and a track record of effective leadership as acting ATF director,” White House spokesman Jay Carney said. “The ATF is a critical law enforcement agency that helps protect our communities from dangerous criminals, gun violence and acts of terror, yet for the past six years it has been serving without a confirmed director because Senate Republicans have blocked every nominee, regardless of their qualifications.”

Jones, 55, took over the agency on an interim basis in 2011, after the Fast and Furious operation was made public. But lawmakers including the panel’s senior Republican, Sen. Charles Grassley of Iowa, have questioned what he knew about the operation before taking over ATF.

Jones chaired an advisory committee to Attorney General Eric Holder from 2009 through 2011, when the operation was in effect. That committee doesn’t have oversight over any law enforcement operations, but Grassley and others insist that Jones should answer questions about whatever he knows of the program that allowed thousands of guns to be smuggled across the border with Mexico and into the hands of some of Mexico’s most violent drug cartels.

The Iowa senator and others have also pressed Jones to answer questions about decisions he made in a false claims case involving the city of St. Paul, Minn. They have accused Jones and the Justice Department of agreeing to drop the case against the city so long as the city dropped an appeal to the U.S. Supreme Court in an unrelated case.

The former head of the Minneapolis FBI office, Donald Oswald, has also written a letter to Congress accusing Jones of impeding federal prosecutions of gang, drug and gun laws.

Oswald said Jones was “substantially motivated by personal political gain and not by doing what’s in the best interest of the citizens he is sworn to protect.”

Jones, who was appointed U.S. attorney in Minnesota in 2009, has declined to discuss Oswald’s allegations and other issues surrounding his nomination. In a statement Monday he said he was looking “forward to meeting with the Judiciary Committee and answering all of their questions.”

Grassley said Monday the Jones’ hearing was “highly unusual, if not unprecedented,” because there is an ongoing Office of Special Counsel probe of his work as U.S. attorney.

The Office of Special Counsel is an independent federal agency that investigates and prosecutes prohibited personnel practices, such as reprisal for whistle-blowing. In April the special counsel notified Judiciary Committee Chairman Patrick Leahy, D-Vt., and Grassley that she was looking into an allegation that Jones retaliated against a federal prosecutor for whistle-blower-protected activities in Minnesota. The specifics of the allegation were not available.

“I take whistle-blowers’ complaints very seriously, and the rest of the committee should, too, and not push a hearing on a controversial nominee with several unresolved issues and a formal complaint pending against him for a position that the president left open, without a nominee, for two years,” Grassley said.

The hearing comes nearly six months after 26 people, including 20 children, were shot to death in Newtown, Conn., spurring Obama and some lawmakers to push for new gun control laws. So far, those efforts have failed. Gun control advocates, including some families of the victims from the Sandy Hook Elementary School shooting, are in Washington this week to again push lawmakers to support expanding background checks for gun purchases. The Senate rejected a bill to do that in April.

The National Rifle Association and other gun-rights advocates have argued that expanded background checks would lead to a national registry of guns and the federal government should focus on enforcing existing laws.

The ATF long has been criticized for perceived failures to prosecute gun crimes, including against those people who lie on federal forms when trying to buy a gun.

According to statistics provided by the ATF, the agency recommended charges be filed against more than 70,500 people from 2009 to 2012. More than 42,000 of those people were eventually convicted of firearms-related offenses.

Four other people have led ATF on a temporary basis since 2006, and two men have been nominated for Senate approval. In 2007 President George W. Bush’s nominee, Michael Sullivan, was given a hearing but his nomination was ultimately blocked.

In 2009, Obama nominated Andrew Traver. The NRA strongly opposed him, saying at the time that Traver “has been deeply aligned with gun control advocates and anti-gun activities.” He never had a hearing.

The NRA has not publicly opposed or endorsed Jones.