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Bloomberg made six-figure donation to Giffords-led group

New York Mayor Michael Bloomberg made a personal six-figure contribution to Americans for Responsible Solutions, the political action committee run by former Rep. Gabrielle Giffords (D-Ariz.) and her husband Mark Kelly, a source close to the mayor tells NBC News.

As First Read reported earlier, Americans for Responsible Solutions will spend six figures to air a new ad beginning this week. The ad will air in DC and in cities represented by congressional leaders: San Francisco (Nancy Pelosi), Cincinnati (John Boehner), Louisville (Mitch McConnell), and Las Vegas (Harry Reid).

Bloomberg has his own group, Mayors Against Illegal Guns, that's pressing Congress to take steps to reduce gun violence. Bloomberg's own Independence PAC has spent nearly $1 million on ads attacking former Democratic Rep. Debbie Halvorson for her "A" rating from the National Rifle Association.

Halvorson is locked in a Democratic primary for former Rep. Jesse Jackson's seat in Illinois.