Republicans took back 4 House seats in deep-blue California. How did they do it?

Rep. Ami Bera (D-CA) in his Longworth Building office in the U.S. Capitol complex in Washington, D.C., on February 11, 2014. (J.M. Eddins, Jr./TNS)

WASHINGTON — Republicans have clinched four of the seven competitive House races in California, proving wrong the dismal projections of their chances in 2020 and setting up the party for possible further success in 2022.

It's a reflection of the rest of the country, where Democrats expected to expand their majority and instead lost a significant amount of seats to Republicans, delivering the narrowest House majority in about a century to Democrats.