Washington – Michael Bloomberg's gun-control advocacy group is running an ad backing legislation from Sen. Amy Klobuchar, D-Minn., that would expand restrictions on handgun purchases by domestic abusers.

In the ad by Everytown for Gun Safety, a man kicks down the door of his ex's house, grabs their crying son and pulls out a gun as the woman calls 911 and tries to stop him. He points the gun at her head, and the ad cuts to a black screen with the message, "Stop gun violence against women," before the sound of a gunshot is heard.

Bloomberg, the billionaire former mayor of New York City, is planning to spend upward of $50 million this year to help Everytown challenge the National Rifle Association and to mobilize voters to back gun-control efforts.

The advocacy group is running the ad on cable TV in Washington and on networks in three states, urging viewers to contact three Republican senators — Jeff Flake of Arizona, Kelly Ayotte of New Hampshire and Dean Heller of Nevada — who voted against a bill that would have expanded background checks on potential gun buyers.

The Senate reauthorized the Violence Against Women Act last year including provisions to strengthen federal stalking laws, but there is "more to be done," Klobuchar said.

Her bill, the Protecting Domestic Violence and Stalking Victims Act, would expand federal law to bar abusive dating partners, individuals under a restraining order and convicted stalkers from buying or owning a gun. Current law already prevents people convicted of domestic abuse from buying or owning a gun.

During a Senate Judiciary Committee hearing Wednesday, Klobuchar said that in states such as Minnesota, that require background checks for private handgun sales, 38 percent fewer women are shot to death by intimate partners than in states that don't have such checks.

The National Rifle Association opposes Klobuchar's bill, which has no Republican cosponsors. The NRA sent a letter to members of Congress this summer saying the measure is an attempt to manipulate "emotionally compelling issues such as 'domestic violence' and 'stalking' simply to cast as wide a net as possible for federal firearm prohibitions."

The release of the Bloomberg group's ad came ahead of the Judiciary Committee hearing to examine steps to strengthen the Violence Against Women Act.

Gun control legislation has been met with strong opposition from congressional Republicans and some Democrats.

The lead Republican on the Senate Judiciary Committee, Chuck Grassley of Iowa, raised questions about Klobuchar's bill and legislation proposed by Connecticut Sen. Richard Blumenthal that would provide resources to states to encourage them to take guns out of the hands of "dangerous people."

Grassley criticized the legislation, arguing that it takes the wrong approach to solving domestic violence problems and would make "individuals who were allowed to own guns criminals retroactively, not by virtue of their crime, but from passing the bill."

Klobuchar acknowledged Grassley's concerns, but said the goal of the legislation is simple.

"This bill is about preventing a person with a documented history of domestic violence or stalking or mental illness from having a firearm. That's it."