Sentence:  Nearing 2.30, stoking fears of a disastrous night for the Lib Dems, the Tories achieved their first "<WSD>decapitation</WSD>" ‑ a visibly shocked Lembit Opik, in once-safe Montgomeryshire ‑ while evading their own biggest risk of high-profile embarrassment: Oliver Letwin held Dorset West. 
Meaning of the word marked with <WSD> tags:  The unseating of a senior politician.