The documentary, "Running With Beto," a behind-the-scenes look at Beto O'Rourke's 2018 Senate campaign is set to debut on May 28

In 2018, Beto O'Rourke staged a grassroots attempt to unseat Ted Cruz and represent Texas in the US Senate. Embedded with the campaign for a year, filmmaker David Modigliani had intimate access to O'Rourke, his tight-knit family and his team of political newcomers, who championed a new way of getting to know a candidate - one Texas county at a time.

"Running With Beto" follows the Democratic congressman's rise from virtual unknown to national political sensation. The film premiered at this year's South By Southwest Film Festival, where it received the Audience Award for Documentary Spotlight.

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As a Democrat in the historically Republican stronghold of Texas, El Paso native Beto O'Rourke's journey was unique. He traveled to all 254 counties in the state, using social media in unconventional ways to convey his message while declining to accept all PAC money or corporate contributions, resulting in the best-funded grassroots campaign in U.S. Senate history.

"Running With Beto" presents O'Rourke in a way he has never been seen before, underscoring the personal and political toll that running for office can take on a candidate and a family, and capturing revealing moments with his wife and three young kids throughout the grueling journey. Along the way, he must battle an onslaught of negative advertising and confront the pressures of delivering for a movement he inspires.

The film offers an inside look at O'Rourke's unorthodox staff and the passionate, diverse supporters helping spread his message in Texas. Among them are Marcel McClinton, a 17-year-old gun safety activist who survived a mass shooting at his church; former Republican Amanda Salas, a gay Latina determined to turn out votes in her apathetic community; and Shannon Gay, a gun enthusiast from a rural military family.

The documentary debuts on Tuesday, May 28 (8:00-9:30 p.m. ET/PT), exclusively on HBO.

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US Presidential hopeful Beto O'Rouke.HBO