Which Ipsos 5/16/09 has a TNS-Sofres 5/28/09 of 2.5%?
CREATE TABLE "polling" (
  "party" text,
  "results_2004" text,
  "csa_5_14_09" text,
  "viavoice_5_15_09" text,
  "ifop_la_croix_5_15_09" text,
  "ipsos_5_16_09" text,
  "opinion_way_5_18_09" text,
  "csa_5_20_09" text,
  "ipsos_5_25_09" text,
  "tns_sofres_5_26_09" text,
  "opinion_way_5_28_09" text,
  "tns_sofres_5_28_09" text
);
SELECT "ipsos_5_16_09" FROM "polling" WHERE "tns_sofres_5_28_09"='2.5%';