The group extended the buy to run for a full two weeks, through Feb. 10, and is spending another $380,000 to air it, according to filings released today.

The extension comes as a recent poll, conducted for former Cook County Administrator Robin Kelly (D), showed Halvorson's support dipping over the past month, putting her in second place in the race.

Kelly sits at 26 percent support, with Halvorson at 22, Illinois state Sen. Toi Hutchinson (D) at 20 and Chicago Alderman Anthony Beale (D) at 10 percent, according to the poll, a sign that Halvorson faces a tough road ahead to win the race.

Even more problematic for Halvorson: Her support has dipped three percentage points since Kelly's campaign first polled the race in early January.

That indicates that the campaign's heavy focus on her opposition to gun control in the heavily urban district is hurting the one-term congresswoman and that her high name identification is unlikely to be enough to pull her across the finish line, and that the race's real front-runners could soon be Hutchinson and Kelly.

Stefan Friedman, spokesman for the Independence USA PAC that is airing the ads, wouldn't comment on whether the group would further expand the buy, but said it will work to publicize her positions on gun control.

"Debbie Halvorson's record, particularly on the issue of gun safety, is one we think voters in and around Chicago should hear about because it is outside the mainstream. And we've been clear that we're going to work to make that known," he said.