A chapter asking prospective volunteers to run only for an office represents the traditional approach. But, probably, many tend to view this as all or nothing. That is, (s)he would have to commit year-round or not at all. There is an alternative -- offer more choices and greater flexibility.
But how? First, the chapter needs to identify and fill, minimally, each critical position prior to the election. Also, on Election Day, willing members on the slate -- especially incumbents -- agreeing to announce their intent to step aside and take on a different activity, facilitates volunteerism. Otherwise, a prospective candidate may feel intimidated by the incumbent's experience and defer.