To espouse an ideology, belief, etc., is to take it up and support it as a cause. Espouse is usually encountered in formal speech and writing.

// The article explores some of the lesser-known viewpoints espoused by the charismatic leader.

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“Crammed into a tiny apartment in Greenwich Village, they [Yoko Ono and John Lennon] immersed themselves in the city’s counterculture, absorbing progressive politics whenever they weren’t glued to the television set. Lennon’s celebrity secured the duo a large platform to espouse these ideas ...” — Stephen Thomas Erlewine, Pitchfork, 11 Oct. 2025

As you might guess, the words espouse and spouse are hitched, both coming from the Latin verb spondēre, meaning “to promise” or “to betroth.” In fact, the two were once completely interchangeable, with each serving as a noun meaning “a newly married person” or “a partner in marriage” and also as a verb meaning “to marry.” Their semantic separation began when the noun espouse fell out of use. Nowadays, espouse is almost exclusively encountered as a verb used in the figuratively extended sense “to commit to and support as a cause.”