Contradict doubter abandoning party in revolution (5)

I believe the answer is:

rebut

'contradict' is the definition.
(I've seen this before)

I can't explain the rest of the clue.

(Other definitions for rebut that I've seen before include "Refute - disprove" , "Give the lie to" , "Overthrow by argument or proof" , "Repel" , "Confute" .)

I've seen this clue in The Independent.

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