A gun control supporter backed by New York Mayor Michael Bloomberg won the Democratic primary to replace disgraced ex-Rep. Jesse Jackson Jr. in Chicago Tuesday.

The billionaire Bloomberg, a champion of tighter restrictions on weapons, poured more than $2 million from his Independence USA super PAC to support Robin Kelly, a former Illinois legislator who backs an assault weapons ban, and attacked her main opponent, former U.S. Rep. Debbie Halvorson, who was supported by the gun rights lobby.

A little over an hour after the polls closed, Halvorson called Kelly to concede defeat, saying that Bloomberg's television attack ads had tipped the race, Reuters reported.

The ads highlighted Halvorson's support from the National Rifle Association, and her opposition to a ban on assault weapons.

"There was $2.3 million minimum spent against me," Halvorson told supporters after she conceded defeat, according to Reuters. "That's the way it is. I can't help it."

Halvorson warned that if the ads were successful Bloomberg would try to “buy seats” across the country. “We can’t let that happen,” she said.

Another candidate, Chicago Alderman Anthony Beale, also took issue with the ads, saying people are “extremely upset” that a New Yorker is trying to tell people in Illinois how to vote and predicting that there will be a “backlash,” the Associated Press reported.

Kelly took 53 percent of the vote, Halvorson 24 percent and Beale 11, the Chicago Tribune reported.

The Chicago primary, in an overwhelmingly Democratic district, was the first electoral test of the gun issue since the Sandy Hook school massacre on Dec. 14.

Chicago’s city's murder rate has risen with a surge of gang violence in poor neighborhoods. The shootings have claimed the lives of dozens of young people including Hadiya Pendleton, a high school student who was killed just a week after she performed at President Barack Obama's inauguration.

Bloomberg issued a statement after Kelly was declared the winner saying that the vote showed Americans want change in Washington.

"As Congress considers the president's gun package, voters in Illinois have sent a clear message: We need common sense gun legislation now. Now it's up to Washington to act," he said.

The special election was to fill the seat of Jackson, who resigned in November citing health problems, and pleaded guilty in federal court last week to using campaign funds for personal enrichment.

Turnout was very light in the special election in part because of a snowstorm that hit the Chicago area on Tuesday, making travel treacherous.

The winner of the Democratic primary is likely to be elected to the seat in the general election on April 9.