Transportation Secretary Ray LaHood speaks in Detroit, in May. (Paul Sancya - Associated Press)

Ray LaHood, the Illinois Republican who turned distracted driving into a national crusade while serving a Democratic president, will step down after four years as President Obama’s transportation secretary.

LaHood is the only Republican in the Cabinet, a mantle that will be carried by former senator Chuck Hagel of Nebraska if he wins Senate confirmation as secretary of defense.

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