The Newark by-election saw centre-left voters hold their noses and back the Tories to stop Ukip.
The party holds the seat with a majority of more than 7,000 as the Lib Dems are pushed into sixth place.
Election strategist Lynton Crosby has warned them that it helps Labour, which has a double-digit lead on the issue.
The Prime Minister should stop indulging the idea that Europe is a conspiracy perpetrated by other countries against Britain.
An ambitious growth plan could be implemented with no public borrowing at all.
It's not up to the unelected commission to determine Britain's policies, but it has reason and evidence on its side.
Lord Ashcroft's poll puts them 15 points ahead of Ukip, but they trail Labour by nine points nationally.
With a week to go, the party's eight-point lead is too small for comfort.
Cameron fears the collapse of the coalition. Labour fears a more popular centre-left leader.
Targets are missed on two fronts, with net migration up by 212,000 and borrowing up by £1.9bn.