McCarthy will be responsible for helping Republican Whip Eric Cantor of Virginia respond to the Democratic majority's legislative agenda, the Los Angeles Times reported Sunday.
"Kevin McCarthy has an affable personality, so he puts a friendly face on the party," said John Pitney Jr., a political scientist at Claremont McKenna College. He called McCarthy a "consensus builder."
McCarthy's district includes much of Kern and San Luis Obispo counties and the Lancaster area of Los Angeles County.
John Feehery, a former House Republican leadership aide, said McCarthy's biggest challenge is "to steer the Republicans from an ideological course to a more pragmatic course that will help make the Republican less toxic."
The Times said McCarthy used his campaign fund to contribute to almost 80 Republican candidates in the last election.
He also raised and contributed more than $300,000 to the House GOP campaign committee.