(CNN) - The powerful National Rifle Association lobby should see Tuesday's outcome in a congressional election as a sign that their influence is declining, New York City Mayor Michael Bloomberg said, predicting future wins for pro-gun control candidates would require less than the $2 million he injected into this race.
"I think it's a harbinger of what is going to happen here," Bloomberg said in an interview to air Wednesday on CNN's "The Situation Room."
Illinois state Rep. Robin Kelly defeated former U.S. Rep. Debbie Halvorson on Tuesday in a Democratic primary for the U.S. Congress that was closely watched nationally because Halvorson had once been endorsed by and scored a top rating from the NRA; Bloomberg's super PAC Independence USA invested heavily in this race; and Kelly has spoken out in favor of gun control efforts.
This primary - to replace the disgraced Rep. Jesse Jackson Jr. - was the first congressional race since the December 14 Newtown, Connecticut shooting which left 20 students and 6 teachers at an elementary school dead and led to calls from President Barack Obama and others for greater gun control.
Bloomberg's group ran ads in support of Kelly and against two other candidates, Halvorson and a second who dropped out, but he predicted his super PAC wouldn't have to spend so heavily in the future for the election to go his way.
He said the election was "a great victory for our kids who are getting murdered on the streets." Despite his massive spending in the race, he told reporters outside the White House on Wednesday that "I didn't win" in the election.
Instead, he said, the election was a sign of public sentiment.
"You don't have to put money into every race," Bloomberg said in the CNN interview. "At the end, the money doesn't matter - it's the people who show up at the polls."
The climate in Chicago - which saw 506 murders last year, up from 433 murders in 2011, local crime statistics showed - may be especially receptive for a gun control message. Obama recently spoke in the city against gun violence and his wife attended the funeral for a teenage gun violence victim who had participated in the festivities surrounding her husband's second inauguration last month.
"The NRA has had the field to itself of talking about guns and it's time for a balanced approach. The public can get the information and then let the public decide," Bloomberg said.
The district where Kelly won includes parts of Chicago's South Side and is considered a likely win for Democrats in the special election on April 9.
Bloomberg urged Congress to pass a number of gun control measures, including the assault weapons ban and a tightening of background check requirements.
"If it can be done as one package [or] if it can be done individually, as long as they get done I think this country will be a lot better off," he said.
He said none of the senators he met with on Thursday - including majority leader Harry Reid and Republicans Susan Collins, John McCain and Mark Kirk - "made a specific commitment," but "I walked away comfortable that they understand the issue and that they will be there."
An earlier version of this story erroneously reported the number of murders in Chicago last year.