Cameron shifts tack as election campaign fails to shift dial

By Andrew Osborn LONDON (Reuters) - British Prime Minister David Cameron's advisers thought his economic record would have delivered a solid poll lead by now. The absence of a breakthrough coupled with a stronger than expected performance from Ed Miliband, the leader of the opposition Labour Party, is dampening the mood in Cameron's centre-right Conservative Party. The campaign has been almost genteel." The election, which could determine Britain's place in the European Union