Swedish backing for the euro overtook the "No" side in a poll for the first time in months after the murder of pro-euro Foreign Minister Anna Lindh.
A Gallup poll taken after Ms Lindh died of stab wounds on Thursday indicated that backing for the European Union's single currency had jumped to lead opposition by 43-42 per cent, on an apparent wave of sympathy for the fervent pro-euro campaigner.
It was the first poll since April to indicate a "Yes" lead in the vote on ditching the crown for the euro, although a survey yesterday had pointed to a 50-50 per cent tie.
Ms Lindh's murder halted all euro campaigning, but Prime Minister Goran Persson and other politicians urged Swedes to vote tomorrow to show that violence would not prevail over democracy.
"Anna Lindh's death is affecting the referendum," said the daily Expressen, which published the Gallup survey of 1,033 people with TV4. It compared to a Gallup poll earlier in the week in which the "No" side had led by 50-35 percent.
But a Temo survey for the Dagens Nyheter daily, also taken after Ms Lindh's death, showed the "No" camp with a 46-40 percent lead. The number of undecided voters had risen slightly from a previous survey showing a "No" win by 48-42.
Many Swedes fear joining the euro could undermine their generous cradle-to-grave welfare despite assurances from Mr Persson that the economy would benefit in the long term. Police have made no arrests since the stabbing in a Stockholm department store on Wednesday but Swedes got a first glimpse of a possible suspect when newspapers showed fuzzy pictures of a man in a cap captured on a surveillance camera.
Tabloids blanked out the face of the dark-haired man, apparently aged about 30, and police were still analysing the store videos before deciding whether to publish.
Police also located a key witness to the killing, a woman dressed in red who had yelled "Catch him!" as the murderer fled down an escalator. "Investigators have made contact with the woman in red," spokeswoman Ms Agnetha Styrwoldt-Alfheim said.
Yesterday, up to 50,000 people - many carrying red roses - staged Sweden's biggest political demonstration since the Vietnam War a few blocks from where Ms Lindh was knifed.