Considering that you're registered on, and posting on a political website, you might want to use the in-context, prevailing definitions that this site uses. Imagine the reaction I'd get if I started posting on Catholic Answers, and insisted on using the term "apostolic" to describe the political belief espoused by Lex, Rex.
It would be fine to use “apostolic” as a sort metaphorical expression on a political blog. People can be described as conservative about all sorts of things: politics, religion, even their haircuts and clothing styles!