IDIOMS

carry water for

(transitive, idiomatic) To perform menial tasks for; to serve; to assist; to be forced by politics or pragmatism to endorse or promote a belief, individual, or organization that in reality one does not fully support.

Example: 1967, Sarah Gainham, Night falls on the city‎, page 558:
  Julie heard a woman's voice saying that she certainly was not going to carry water for any conceited bitches who thought themselves too good for ordinary....
2003, Barbara Ewing, The Trespass‎, page 329:
  For such a caring man she would carry water for the rest of her life: no man of her acquaintance would have done what Edward Cooper did, for a woman.
2006, Larry Bond; James DeFelice, First team: angels of wrath, page 375:
  "We won't get another chance to talk, so tell me, deab: Is Peter the man to carry water for me between the Israelis and the Palestinians, or should I find another horse for that plow.
2008, Ralph Reed, Dark Horse, page 229:
  His job was to watch Stanton's back, not carry water for his ex-boss.