What does the Labour freefall mean for the SNP?

Any lingering doubt that we are living in unprecedented political times was removed by the latest UK-wide YouGov poll showing Labour at an all-time low of 22%. By my reckoning, the combined figure for the 'others' also now stands at an astonishing 18%. On the face of it, good news for the SNP - but is it really? Clearly there's now an unprecedented anti-establishment mood out there, but the jury's also out on whether the electorate will still perceive the SNP as a true anti-establishment party, or whether they'll reserve that for fringe groups like UKIP, the Greens and the BNP. But even if the SNP take a small hit themselves, it surely can't compare with what is happening to Labour - and that being the case the signs are good for victory in the popular vote on June 4th.