I think this claim is false.  A quick google search of the NAE website <http://www.nae.net> with the search term "30 million" leads to a few hits, most of which when clicked lead to 404 errors, meaning they are not currently featured on the website.  The only one that is current is an endorsement from evangelical pastor Joel Hunter.

Additionally, in her book The Fall of the Evangelical Nation, religion reporter Christine Wicker attempted to track down the source of the claim that the National Association of Evangelicals had 30 million members, but could not substantiate it with any reputable sources or hard numbers.

In the chapter entitled, "One Out of Four Americans?" she writes (page 26):

When I called NAE president Leith Anderson in August 2007 for a final comment, he said the 30 million figure should not be on the Web site, and most references to it do appear to be gone now.  He usually says the NEA represents millions of evangelicals or forty-five thousand churches.  The organization's last official count, judging by its Web site, was in 1990.  It showed 4.5 million members.  Where did the 30 million figure come from?  No one seems to know.

Wicker, C. (2008) The Fall of the Evangelical Nation. New York: HarperOne

However, the "About Us" portion of the NAE website feature does feature NAE president Leith Anderson stating, "The association is anchored in over 40 denominations with about 45,000 churches. However, the broader NAE constituency includes organizations, local churches and individuals numbering in the tens of millions."  What exactly Anderson means by the "broader NAE constituency" (i.e. which affiliated organizations is he talking about, and what does he mean by local churches and individuals who are not in the NAE proper, but in the "broader NAE constituency?") is not explained with any precision, unfortunately.

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"I believe in a President whose views on religion are his own private affair" - JFK, Address to the Greater Houston Ministerial Association
by hardindr on Fri Nov 13, 2009 at 05:46:43 AM EST