To "throw (someone) under the bus" is an idiomatic phrase in English meaning to blame or abandon a person for selfish reasons.
[1][2] The earliest known usage of this phrase was 21 June 1982, when Julian Critchley of The Times (London) wrote "President Galtieri had pushed her under the bus which the gossips had said was the only means of her removal.
"[3] After Julian Critchley, a relatively early use is attributed by the website Double-Tongued Dictionary[4] to a 1991 article in the Colorado Springs Gazette-Telegraph.
It has frequently been used to describe various politicians distancing themselves from suddenly unpopular or controversial figures with whom the candidate has previously allied themselves.
[9] In a March 2008 NPR report, the linguist Geoff Nunberg noted that the expression "has appeared in more than 400 press stories on the campaign over the last six months".