On todays Up with Chris Hayes, the host unveiled a 2008 talk by Rick Santorum.
The speech is from a 2008 event at Ave Maria College in Florida, where Santorum notes that America was founded upon a Christian philosophy but the Judeo-Christian ethic was a Protestant one. We look at the shape of mainline protestantism in this country and it is in shambles, it is gone from the world of Christianity as I see it
These people tended to belong to a fixed group of Protestant, or allegedly Protestant churches ~ the Episcopaleans, Dutch Reformed, Presbyterians, that sort. Old money, old families, old everything. Your more ordinary people were Baptists, Catholics, Methodists, Lutherans and so on. They didn't live along the Mainline.
It's the term "Mainline", not "Protestant" that's operative in that particular statement, and it is very true that the Mainline churches which were owned and operated by the very rich are in serious trouble. They're being taken over by homosexuals and non-Christians. Those who can, escape to other up and coming denominations, or even into the Catholic church.
Doesn't PO me at all to hear Santorum criticize the MAINLINE ~ they deserve it. They no longer hold the Mandate of Heaven ~ that's moved on to other more worthy Christians.
BTW, your understanding of American cultural history is just horrid. You could pick up any number of standard textbooks used in universities and get over this. Find one that has MAINLINE in the index, and check and see if that refers to religious bodies or heroin. Big difference eh! But it's a clue.