The purpose of the coup would be to reverse the legislative before it becomes law.
They believe that a sufficient number of Labour MPs would cooperate in order that the Liberal Democrat vote is countered and the bill can be struck off before it reaches the statute book.
They realise that an election would be the inevitable outcome arising from the combination of minority government and a prime minister without mandate. However, they be believe that this is a price worth paying, since they believe that the Conservative Party will never achieve majority government again, if AV is implemented.
David Davies is already campaigning for a future leadership bid, by creating a manifesto and inviting back-benchers to contribute a policy. Those that make a contribution effectively endorse him as candidate. Included in this pseudo manifesto is a promise to slow down the deficit reduction program in order to avoid recession. An interesting insight to their true thoughts.
At this point it is not know which other Conservative MPs would also run.
With the No 2 AV camp apparently uninspired by the debate; there is a strong chance that they will suffer a low turnout, while the enthusiastic Yes 2 AV camp is highly likely to vote, meaning the odds are on for a Yes win.
For further details on resentment in the Conservative Party towards David Cameron, read my previous post, The Cameron Collapse Scenario.
This plot considerably increases the drama of a so-far bitter, but dull referendum debate.