Contrast reneging on Lisbon with sticking to his guns on AGW during climategate - probably loosing votes in both cases. Vote don't matter that much - the Kinnocks never had to win an election to get where they got.
Voters don't matter much where AGW and the EU are concerned, because the major parties are pretty well in agreement. Apart from the parties, which are the froth on the surface, there's a powerful establishment in favour of these things which would strike back. I never thought the Tory position on the LT was other than making a commitment they knew they were unlikely to have to live up to, for tactical reasons.
I think there's much in what you say. Being out of office would be preferable to being in office on the condition that they were going to have to confront the EU and dismantle the structures put in place to deal with climate change. Especially when the Euro elections are coming round, the Tories like to play the three nutshells and pea game with their position on the EU.