Sentence:  When asked by Duffy about rumours that he was being heavily courted by the Tories to <WSD>cross the aisle</WSD> and join them, Kilgour replied that they've opened "No doors." 
Meaning of the word marked with <WSD> tags:  Of a member of a parliament, to resign from one's political party and join another party, resulting in moving from one's currently assigned desk or seat in the legislative chamber to a new desk or seat physically located with the other members of one's new party.