"If the Lib Dems were planning on dumping the Tories, this is how they'd do it ..."

[T_i_B]

4. "collapsed" is the wrong word.

It appears very much that the Tories have fielded a paper candidate in Hallam. That is, a candidate who's on the ballot paper and does the bare minimum beyond that.

This in turn has allowed Clegg to use such things as the "Harthman letter" (a letter from a previous Tory candidate in Hallam endorsing Clegg) to run as a surrogate Tory in an area which is affluent and conservative by nature.

The Lib Dems have also been flinging resources at Hallam while ignoring everywhere else in the area. For instance, I live in a neighbouring constituency and our Lib Dem candidate is a paper candidate who doesn't bother turning up to hustings meetings.

But by the same token, the constituency where I live is fairly marginal at present, and not bothering in Sheffield Hallam allows the Tories to fling more resources at winning in the Constituency where I am.