The campaign to keep Scotland in the UK has a nine-point lead over its rival, according to a poll.
The Panelbase survey suggests support for the union stands at 46%, up two points from May, while support for independence rose one point to 37%.
But in a warning to the Better Together movement, the results show pro-independence supporters are more likely to take part in the ballot in September 2014.
Ivor Knox, managing director of Panelbase, said: "If we include everyone who has told us which way they plan to vote, irrespective of likelihood, the No side has a more substantial lead of 58 to 42."
The poll of 1001 adults in Scotland found that 94% of independence supporters were very likely to take part, compared with 87% of unionists. Meanwhile, the SNP has seen its support increase by three points to 48%.
Among other constituency voting preferences, Labour support is unchanged at 30%, Conservatives remain on 13% and the Liberal Democrats slip by one point to 4%.
Regional voting intentions put the SNP up three points to 48%, Labour down two points to 25%, Conservatives unchanged at 13%, Greens still on 6% and the LibDems dropping two points to fifth place on 4%.
SNP party business convener Derek Mackay said: "This is an extremely encouraging poll. With just a single-digit gap between Yes and No, a swing of less than 5% is enough to put independence ahead.
"There is everything to play for. Yes supporters are more likely to vote than people currently on the No side."
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