They set it up as an all or nothing vote, specifically leaving an option for autonomy of the Scottish independence referendum, and now that the polls are showing independence having a (small) lead, Chancellor of the Exchequer George Osborne has issued a statement saying that they intend to increase autonomy:

A last-minute all-party plan to devolve further powers to Scotland over tax, spending, welfare and a host of other areas will be unveiled in the next few days, George Osborne has said.

The announcement came after a YouGov poll showed the yes side taking a narrow lead, spreading fears at Westminster of a constitutional crisis.

The chancellor detailed the plans – the product of backroom talks – saying they would be unveiled in the next few days with a clear timetable for implementation in the event of a no vote. The offer is similar to the last-minute package offered to Quebec by the Canadian government in 1995, that staved off a vote for separation.

All the major political parties have presented different offers of further devolution, but there has been no agreement between them on far they should extend.

The announcement of the package also represents a shift away from the negative tone of the previous no campaign to a positive offer of the benefits of staying inside a United Kingdom. Many polls show support for wider devolution but there has been a lack of clarity about what it represents in practice.

The political parties said it was unlikely the joint statement would set out detailed new powers beyond those already promised, but focus on a credible timetable and process for the transfer to come about. The three parties have already issued a joint statement of further transfer of powers in June but, judging by the latest polls, this may have had little effect.

No specifics, of course, because they really do not want to allow Scotland to have authority on taxes and social welfare programs, because this would provide a nearby case study for the futility of benefit and tax cuts, but it appears that political reality is that some sort of retreat is essential for the Conservatives to defeat this referendum.

Still, I would not trust them do keep their word if I were a Scotsman who had to make up his mind about how to vote.