WASHINGTON — The top television executive at the Corporation for Public Broadcasting announced on Thursday that he would be stepping down. This is the latest in a string of departures of officials and consultants who played central roles in an effort by conservatives to bring what they viewed as more balance to public television and radio. The executive, Michael Pack, controlled a $70 million production budget and was described by the official who hired him as a conservative Republican. He chose to resign after Patricia S. Harrison, the corporation’s new president, forced him to decide between renewing his employment contract and exercising a soon-to-expire option that gives him $500,000 to produce a documentary. Ms. Harrison said the departures of Mr. Pack and a senior consultant, James Denton, were business decisions and were not part of any purge of ideologically driven officials. “You are connecting dots when there is no connection,” she said in an interview. “I have not fired a single person since I came on board here.” But other officials in public broadcasting saw political overtones to the moves. Since being named president of the corporation last June, Ms. Harrison, a former co-chairwoman of the Republican […]