Lib Dem leader is trailing Labour in Sheffield Hallam constituency . Deputy Prime Minister won his seat in six weeks with more than 50 % of the vote . Revelation included in latest round of polling in marginal constituencies .
Lib Dem leader is trailing Labour in Sheffield Hallam constituency . Deputy Prime Minister won his seat in 2010 with more than 50 % of the vote . Revelation included in latest round of polling in marginal constituencies .