premise: The summoning of politicians came after prosecutors pledged a new probe into politicians whose names have surfaced in the course investigations into the massive loans-for-kickbacks scandal engulfing Hanbo.
  The prosecution had said that aside from the arrested four, they had no plans to investigate other politicians who allegedly took customary "rice cake expenditures."
  Rice cake expenditures are cash gifts of anywhere between tens of dollars and tens of thousand dollars, which are offered with no clear strings attatched.
  The prosecution's reversal in policy triggered charges of political conspiracy from both the ruling and opposition camps.
  Second opposition party leader Kim Jong-Pil accused the investigation of being "a ploy to protect (South Korean President Kim Young-Sam's second son) Kim Hyun-Chul."
   What does the scandal involving the politicians refer to?
hypothesis: politicians who allegedly took customary "rice cake expenditures