This is Cameron's big opportunity to break free from his right wing

The Conservatives' failure to win an outright majority suits Cameron very nicely.

With a tiny majority, Cameron would have been held hostage on every vote by a squad of trouble-making Tory right-wingers.

With a Lib-Con pact, Cameron can afford to ignore his right wing - the Lib Dems can bail him out even if a dozen right wing head-bangers turn against him.

I think this suits Cameron very well. He's instinctively much more liberal than the bulk of his party. I don't think he gives two hoots about promoting marriage through the tax system - that policy was a sop to his right wing which he will now be able, and more than happy, to ditch.