Why it matters: Nunes, once considered a moderate member of the party, became one of the fiercest defenders of former President Donald Trump throughout both of Trump's impeachments and the Intel committee's Russia investigation.
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Trump awarded Nunes the Presidential Medal of Freedom in 2021.
In a letter to his constituents, Nunes said he was "presented with a new opportunity to fight for the most important issues I believe in," CNN reported.
Driving the news: Nunes will become CEO of "Truth Social" in January.
He will run the company as regulators are investigating the planned merger between Digital World Acquisition Corporation and Trump's company, according to a recent filing by the SPAC.
California's new congressional districts put Nunes in a district that leans more Democratic, per a draft of the map, SFGate reports.
Nunes has served in Congress since 2002.