HOUSTON  Just before he was executed in 2004 for setting a fire that killed his three children, Cameron T. Willingham declared, “I am an innocent man convicted of a crime I did not commit.” Now his words seem to be echoing in the race for governor of Texas.

In what some opponents say looks like a political move and Gov. Rick Perry says was “business as usual,” the governor replaced the head of the Texas Forensic Science Commission and two other members on Wednesday, just 48 hours before the commission was to hear testimony from an arson expert who believes that Mr. Willingham was convicted on faulty testimony, a conclusion that has been supported by other experts in the field.

Mr. Perry’s decision to shake up the commission and put one of his political allies in charge has, at the least, delayed the inquiry into the Willingham case. While Mr. Perry says he has no political motive for the move, his opponents have called for the commission to finish its inquiry.