(CNN) Speaking at the official launch of her presidential campaign on Sunday, US Sen. Kirsten Gillibrand singled out the National Rifle Association as an example of special interests taking priority over the will of the people.

"Right now, special interests are displacing the voices of the people of this country. Find me a so-called unsolvable problem, and I will point you to the greed and corruption in the way," Gillibrand said, speaking in front of Trump International Hotel in New York. "The NRA stops popular, common sense gun reform, while stray bullets kill children in our communities."

But during her tenure in the US House of Representatives from 2007-2009, then-Rep. Gillibrand fought vigorously in defense of gun rights, including the right to own handguns. While in the House, the New York Democrat represented a more conservative, rural district, compared to the more liberal statewide constituency she represents as a senator.

Gillibrand's position, which was politically advantageous at the time in earning the endorsement of the NRA in her 2008 re-election bid, could now prove a political liability in the 2020 Democratic primary.

Gillibrand has said she regrets her past positions and frames her views on guns at the time as supporting hunting rights.

"On guns, I should have done more, I regret not caring about other communities," Gillibrand said at an MSNBC town hall last week. "My community didn't have the gun violence that other parts of the state had, and, in fact, the biggest issue for upstate New York was hunting rights."

But Gillibrand's advocacy extended beyond hunting rights. She signed an amicus brief that argued for overturning a handgun ban in Washington, DC, and that private gun ownership was a guaranteed right unconnected to service in a militia.

The amicus brief was submitted to the US Supreme Court while the court was hearing the 2008 landmark case, District of Columbia v. Heller. The court ultimately repealed the city's strict gun control laws in a sweeping victory for gun rights advocates.

In addition to Gillibrand, the brief was signed by then-Vice President Dick Cheney, 55 senators (46 Republicans and nine Democrats) and 250 House members (183 Republicans and 67 Democrats).

Gillibrand ultimately campaigned on her pro-gun record when running for re-election in 2008, with the NRA citing her support for the amicus brief in its endorsement of her.

The plaintiff in the DC case, Dick Heller, was a special city police officer who was authorized to carry a handgun while on duty but denied a license for a handgun in his home.

The court ruled in his favor and found that the city's laws banning handguns and requiring firearms in the home be disassembled or bound by a trigger lock was unconstitutional and a violation of the Second Amendment.

The Second Amendment states: "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed." However, there has long been fierce debate about the phrasing of the amendment and what it means by "a well regulated militia."

The brief signed by Gillibrand argues forcefully against the idea that it was meant to protect gun rights for militias and not private individuals, stating, "The Second Amendment guarantees an individual right to keep and bear arms. Recognition of that right promotes the well regulated militia necessary for a free State's security."

The brief also bolstered its defense by tying the idea of an individual's right to own a gun with civil rights for African Americans. It argued that the court should consider that after the Civil War, Congress passed the Civil Rights Act of 1866 and the Freedmen's Bureau Act of 1866 to guarantee rights to recently freed former slaves. Both acts declared black persons to have the same rights as white persons, including the right to bear arms

The court's ultimate ruling required that DC must permit Heller to register his handgun and must issue him a license for it, while also finding unconstitutional the city's law that rifles and shotguns be kept "unloaded and disassembled or bound by a trigger lock."

At the same time the Heller case was moving through federal courts, Gillibrand co-sponsored legislation that would revoke the city's gun control laws. The proposed bill, however, went much further in restricting the city's ability to write its own gun laws than the court's ultimate decision. The core of the proposed bill , called the "District of Columbia Personal Protection Act," made it so that Washington, DC, would not be allowed to pass any laws restricting firearm usage and ownership that exceed existing federal rules.

The pro-gun bill also would have repealed the city's ban on semi-automatic weapons, most registration requirements for possession of firearms and a ban on owning ammunition. These aspects weren't addressed by the Supreme Court.

Like the amicus brief, the District of Columbia Personal Protection Act was disproportionately supported by Republican members of Congress. A total of 184 Republican members of the House ultimately signed onto the legislation as co-sponsors compared to 64 Democrats. The bill died in committee and never made it to the floor for a vote.

"As a strong supporter of the Second Amendment, it is a privilege to have the endorsement of the NRA and the support of Upstate New York's gunowners and hunters," Gillibrand said at the time.

"Congresswoman Kirsten Gillibrand has earned the endorsement of the NRA's Political Victory Fund (NRA-PVF) by consistently voting for the rights of law-abiding gun owners and hunters in the 110th Congress," said Chris W. Cox, chairman of NRA-PVF and NRA's chief lobbyist. "She believes that the Second Amendment is an individual right and she co-signed the congressional amicus brief in support of our individual right to keep and bear arms in the historic Heller case earlier this year. We are pleased to endorse this friend of freedom and fully support her reelection."

After her appointment to the Senate in January 2009, Gillibrand moved sharply and quickly away from her conservative record on gun rights. She points to a visit in February of that year with the parents and classmates of Nyasia Pryear-Yard, a 17-year-old high school student who was shot and killed in a club as transformative.

Gillibrand vowed to take action to stop gun violence.

"There's a very big difference between making sure hunters can hunt in upstate New York, because it's part of our heritage and our history and the Second Amendment to our Constitution, and fighting against gun violence," Gillibrand said at the time . "And those are values and views that I've always held — that we do need to fight against gun violence. We do need to keep guns out of the hands of criminals."

By September 2010, her NRA grade changed from an "A" to an "F." Meredith Kelly, Gillibrand's communications director for her presidential campaign, said she proudly earned the NRA's repudiation.

"Senator Gillibrand proudly earned an 'F' rating from the NRA a decade ago, and has been a passionate advocate for critical reforms to address the scourge of gun violence across our country ever since," Kelly told CNN's KFile in an email.