Now the man from the rural Central Valley of California is running one of the most scrutinized, complex and politically fraught congressional investigations in recent memory.
As chairman of the House intelligence committee, which holds its first public hearing on Monday, Nunes is at the helm of a probe of Moscow's meddling in the 2016 campaign and the murky web of contacts between President Donald Trump's campaign and Russia.
It's a potentially sprawling enterprise that spans continents, plumbs spycraft and dominates international headlines.
He's a long way from raising cattle.
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Until recently, the soft-spoken 43-year-old dubbed a "normal dad" by friends was hardly a fixture on the national news circuit.
Now he is holding weekly press briefings and being asked to weigh in on daily twists and unexpected developments.
At Monday's hearing he will call FBI Director James Comey as a witness, an event that amounts to must-see television in Washington.
Nunes was not an early Trump backer, but was named to the transition team as an adviser on appointments.
On the other side of the aisle, Democratic Sen. Mark Warner, of Virginia, has said the Senate intelligence committee investigation, which he is co-leading, is probably the most important thing he will do in his public life. Nunes says he does not feel the same way.
"Everything we do around here is really important," Nunes said. "I wouldn't put one in front of the other."
Nunes is a third-generation Portuguese-American, and he grew up working on his family's dairy farm. As a teenager, he raised cattle and saved money to buy farmland with his brother, according to his congressional biography. He has degrees in agriculture and keeps his hand in farming through an investment in two California wineries run by a friend he met through his alumni network.