The big question is what changed Michael Martin's mind. I suspect that both Brown and Cameron withdrew support. But I'd argue that Cameron should have done so last weekend in public as Nick Clegg did. And, come to think of it, I agree with the LibDem proposal that all capital gains on property bought with mortgages funded by the taxpayer should be returned to the taxpayer. I can't help thinking that Cameron is being out-flanked on the need for radical reform by Cable and Clegg. Cameron could of course argue that this all is a serious constitutional issue and should not descend into a competition to see who can be rudest about the Speaker. But Cameron badly needs to present the Tories as a radical, purifying force (as so many thought New Labour would be before they got into office). Cameron has a major problem that so many of his MPs have been getting taxpayers to pay for dredging their moats and the like. Cameron needs to compensate for this.
Cameron needs to be seen as the major reformer, and IMHO he missed a trick in calling for a general election rather than for the Speaker's head. And if it was Gordon Brown who called for the Speaker to go, then it will give our beleaguered PM a little bit of kudos. Anyway, enough speculation. We'll find out what happened soon enough.