You could use custom tabs to highlight a basic email signup form, and maybe a hot petition around your issue. (epolitics.com)
Other noteworthy aspects of the site: a supporter list, clear email signup form on the front page (if possible, better to have it on every page), a list of upcoming events, and even a brief tour of Zimon yard signs in their natural habitat. (epolitics.com)
C'm on kids — nonprofits have known to put a clear email signup form or button on every page for years. (epolitics.com)