The party conferences are among the few political events that can have a visible effect on the polls (the Budget, which led to a sustained fall in support for the Tories, is another) and Labour has duly won a bounce from Ed Miliband's well-received  speech . The latest YouGov poll  gives the party a 14-point lead over the Conservatives, up from nine points before the speech and the joint-largest lead it has enjoyed since the general election. Labour's share of the vote has increased by three points to 45%, while the Tories' has fallen by three to 31%. If repeated at an election on a uniform swing, these figures would see Miliband enter Downing Street with a majority of 130 seats.
The Tories will derive some consolation from the fact that Cameron continues to lead Miliband as the "best Prime Minister", but his advantage has shrunk to four points (31-27), the lowest since Miliband became leader.
Further evidence that Miliband's speech has improved his standing is supplied by a Survation poll for the Daily Mirror . The number of people who view him as "statesmanlike" has risen from 18% to 34%, whilst his net approval rating has improved from -46 to -15. In addition, 30% said they were more likely to vote for Labour following his speech (a figure that is more impressive than it appears. Some Labour voters will have needed no further persuasion.)
It remains to be seen whether this is a temporary or a permanent shift, but the Tories can no longer dismiss Miliband as unelectable (if they ever could). Nick Clegg's veto of the boundary changes means that Labour needs a lead of just one point  on a uniform swing to win a majority. Based on the Tories' current performance, it's increasingly hard to see how they could prevent such a result.