The House Republican working behind the scenes to rein in his party's ambitions to cut Medicaid spending is a California dairy farmer who represents more Medicaid beneficiaries than any of his GOP colleagues.

That clash — with the White House on one side and GOP hard-liners in Congress on the other — is now playing out in closed-door meetings and in the hallways of Capitol Hill as the party rushes to write the megabill and potentially cut more than a half-trillion dollars from the safety-net health program over the coming decade.