It's usually used with politics. Both political parties have traditionally espoused free trade. The candidate's popularity rose after he started espousing more social spending.

It means more 'support' or 'promote' rather than 'defend'. - 'Honesty' is a value that we espouse. - The government always espoused it had an interest in what people thought. It is not a term you will hear in conversation (no one has ever said it to me and I've never used it) or everyday print like daily newspapers. It's a rather formal word you'll only see in formal writing, journals, reports or literature.