Charities, Associations, and Lobbying

I am participating in an interesting discussion on the American Society of Association Executives (ASAE's) discussion list for executive directors. To what extent can a charity lobby, and how is it different from an association's lobbying?

Here's part of one post:

...most 501(c)3s, and most people, for that matter, define the term "lobby" too narrowly. It is entirely legal and appropriate for a charity to spend a substantial part of their time and budget in advocacy and public education/information (assuming such activities are part of their stated missions).

OMBWatch did a study on this topic a few years ago called the "Strengthening Nonprofit Advocacy Project" or "SNAP." Here's a link to the executive summary, which includes links to a press release and PowerPoint presentation:
http://www.ombwatch.org/article/articleview/769/1/101/

I also reviewed two books on nonprofit political action for the current issue of the journal "Nonprofit Management and Leadership" (http://www.josseybass.com/WileyCDA/WileyTitle/productCd-NML.html). I can send my copy to anyone who would like it. The books are "Hardball Lobbying for Nonprofits: Real Advocacy for Nonprofits in the New Century," by Barry Hessenius and "Lobbying for Social Change, Third Edition," by Willard C. Richan.