The Bradys' victories may offer winning strategy ideas for Giffords and Kelly.

"Far be it for me to give them advice," said Sarah Brady, now 71. But she's found it helpful to "let members of Congress who are straddling the fence know that public opinion is with you. Make it an embarrassment if they don't do the right thing."

The Brady Law has kept deadly firearms out of the hands of more than 2 million people who failed background checks, according to Brady's group.

Giffords and Kelly say they want Congress to expand the law to require background checks for all gun buyers. Brady agrees.

"We can pass something very, very quickly in the area of background checks," Brady said. "But there are a lot of things that could derail it. With so much of the media everywhere and so many things going on all the time, none of us have the attention span we used to have to stay on one subject. If something new happens, then the discussion will move somewhere else. We've got to stay focused and stay on task and do it quickly."

Brady is optimistic that Congress will vote to expand background checks on firearms purchases. "I think it can be done," she said. "Do I think it's going to be done? I'm not sure. It's going to depend on people like Jim and me and Gabby and Mark."