Analysts caution against reading too much into a single poll, but the latest result comes shortly after a poll by Survation that suggested support for independence had surged since a televised debate in which Alex Salmond, Scotland's first minister, was generally seen as having outmatched Better Together leader and former chancellor Alistair Darling.
Angus Robertson, Scottish National party member of the U.K. parliament, said the poll confirmed surging enthusiasm for independence. "[The] grassroots campaign is delivering momentum," Mr Robertson tweeted.
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With undecided voters excluded, YouGov now puts the No camp's lead at 53 per cent to 47 per cent for No – the same level reported by Survation. The new survey left the poll-of-polls collated by the What Scotland Thinks website at an equal record high of 55 per cent for No to 45 per cent for No.
"McSqueaky bum time" said the Sun, adapting a phrase coined by Scottish football manager Sir Alex Ferguson to illustrate the nervousness of matches in the late stages of a closely fought championship.
The YouGov poll suggested increasing doubts among voters about the future of Scotland's National Health Service if it stays in the U.K. and that many believed U.K. political parties' rejection of a post-independence currency union was mere bluff.
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Better Together has been mocked in recent days for a campaign advert featuring a woman with little apparent knowledge of the independence debate. On Monday, it unveiled a new line of posters that features people saying they would vote against independence because they loved their families.
Despite the narrowing polls, the U.K. government on Monday reiterated that it had not prepared any contingency plans for a Yes vote on September 18.