ProPublica reporter Alec MacGillis won this year’s George Polk Award in the National Reporting category, for his portfolio of stories on the roots of the 2016 political season – including prescient reporting on the revolt of the white working class. This marks the fifth Polk Award for ProPublica.

MacGillis’ on-the-ground reporting in the U.S. heartland measured the region’s gathering wave of discontent, frustration and anger. In “The Great Republican Crack-up,” co-published with Politico, he showed how Dayton, Ohio, transformed from a longtime base for political moderates into a Donald Trump stronghold. The people and events he profiled encapsulated the demographic and socioeconomic changes, including deindustrialization and a growing disaffection with both parties, that contributed to the political shift.

In “’White Trash’ – The Original Underclass,” an essay co-published with the Atlantic magazine, MacGillis analyzed two 2016 books on the history of the white working class.

After the election returns rolled in on the evening of Nov. 8, it took MacGillis just hours to pound out a post-election piece of deeply reported analysis – “Revenge of the Forgotten Class” – explaining how Hillary Clinton and the Democrats were playing with fire when they effectively wrote off white workers in the small towns and cities of the Rust Belt.

Complementing his work on the ground, MacGillis published several other stories that showed how and why the political parties have moved away from their roots. He showed how Washington blew its best chance to fix the nation’s broken immigration system. And he unraveled exactly why a tax break for hedge funds and private equity titans survives in Washington even though it is almost universally derided as an unfair loophole for billionaires.

See a list of all of this year’s Polk Award in Journalism winners here.