which the article references - the meaning that Salzell attributed to it when he coined the term in his book "The Protestant Establishment".
That is to say, old-money, Anglican/Presbyterian, predominantly Anglo-Saxon Northeastern WASPs.
Whilst the Roosevelts were Dutch, they were also Anglican. The same is true for many of the other families.
I think it was Roosevelt that once said that the Anglican church was the Republican party at prayer. To a large extent this is still true. George Bush was raised Anglican, so was John McCain.
I am aware that the Anglican church in America is usually called the Episcopalian church, so perhaps the nomenclature confuses you.
I am also aware that the term has taken on a wider meaning quite distinct from that which Salzell attributed to it, that is to say any generic white person, whether or not they are rich, Anglo Saxon, or even Catholic.
Nevertheless, the original meaning still has wide currency. For example, Jamie Johnson usually writes on WASP issues for Vanity Fair. You can read one of his articles here, but there are quite a few of them:-
http://www.vanityfair.com/online/daily/2008/04/the-decline-of.html