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Iowa Republicans caucus tonight to voice their judgment on which candidate should challenge President Obama for the nation's top job in 2012.

Join us for live special coverage on-air tonight from NPR beginning at 8 p.m. and follow the latest from NPR on Election 2012 below.

Want to know more about the Iowa caucuses? NPR's Political Junkie Ken Rudin wrote up a blog post to give a historical perspective on what winning the caucuses means to the election as a whole and the process of caucusing itself.

Election 2012 News From NPR

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NPR and the Center for Public Integrity are making public for the first time a watch list of the chronic violators of air pollution rules. The list was created in 2004 to help Washington crack down on long-term violators that states and regional EPA offices had failed to bring into compliance with the Clean Air Act. NPR and CPI are the first media outlets to obtain and publish the list, as NPR's Elizabeth Shogren reported today on Morning Edition.

Below is a localized version of the map NPR put together that plots more than 17,000 sources of air pollution across the country. You can interact with the map by zooming in and out and clicking on each colored dot to learn more. You can view the full searchable map, and learn more about the data, using the link below.