I think it's for political reasons and not "faith".
Typically "Evangelicals" are social conservatives like Mormons - as opposed to mainline Protestant churches (Episcopal, Presbeterian, etc) that are pretty-much sold out to the Liberal agenda.
And I guess Roman Catholics, although the Church is officially pro-life, pro-family, etc, many of the adherents are socially liberal (except Freepers, of course).
The main Protestant church in Germany (Lutheran/Calvinist) is called evangelisch.