In an alarming blow for Ed Miliband, the Conservatives have surged in popularity to draw level with Labour in the polls for the first time in more than a year, according to an ICM survey for The Guardian.
And Ukip support, which only months ago made wall-to-wall headlines, appears to have collapsed.
The poll registered a seven-point surge for the Tories to put them on 36% - the same as Miliband's party, who were unchanged on the previous month.
While the past few weeks have seen Labour put through the wringer over their links with the unions as well as some signs of good news for David Cameron on the economy, the bounce for Tories seemed to result largely from a collapse in support for the UK Independence Party.
The Eurosceptic party was backed by just 7% of those questioned, down five points on the previous month and below half the 18% support they recorded in a poll by the same company in March. Ukip's decline allowed the Liberal Democrats to regain third slot, rising one point to 13%.
It is the best result for the Conservatives in a mainstream poll since March 2012, when ICM gave them a three-point lead ahead of George Osborne's much-criticised Budget.
The ICM poll showing Labour and the Tories tied may be an outlier, but try concisely summing up Labour’s message and the problem is obvious.— Owen Jones (@OwenJones84) July 15, 2013
Today's Guardian ICM poll has Tories neck and neck with Labour as UKIP slumps. But is that a rogue poll or harbinger of polls to come?— Andrew Neil (@afneil) July 16, 2013
All eyes will be on surveys over the coming days to see whether Tuesday's result is merely a "blip" or reflects a lasting shift in voter support.
ICM Research interviewed a random sample of 1,003 adults by telephone on 12-14 July.