Houston firefighters are accusing Mayor Sylvester Turner of standing between them and a voter-approved pay raise by failing to ensure a petition they submitted last month is certified in time to appear on the November ballot. Turner rejected any suggestion that he has involved himself in the City Secretary's effort to verify their petition, and his office on Thursday said an offer by the fire union to cover any staffing costs needed to count their signatures is being examined as a possible attempt to improperly influence a public official. At issue is a petition that calls for firefighters to be given "parity" in pay with police officers of corresponding rank, which comes as the union is suing the city over stalled contract talks. Firefighters have been without a contract for three years, and have accused each of the last two mayors of negotiating in bad faith.