MSPs in Holyrood are widely expected to back Nicola Sturgeon's call for a second independence referendum in a key vote on Wednesday evening.
The vote will come at the end of a two-day debate over whether Mrs. Sturgeon should lobby Westminster to hold another referendum between autumn 2018 and spring 2019.
However, there could be a spanner in the works in the form of Theresa May, who has indicated she will refuse any request for a new vote by saying "now is not the time."
On Tuesday, the Scottish First Minister told Holyrood it would be wrong for Westminster to block the vote.
She said: ''In the circumstances we face, for the UK Government to stand in the way of Scotland even having a choice would be wrong, unfair and utterly unsustainable.''
Furthermore, her request could be blocked by Scottish Conservative, Labour and Liberal Democrat politicians, who have already made clear in no uncertain terms they will vote against the motion.
Scottish Conservative leader Ruth Davidson said: ''This referendum may be the First Minister's priority. It is not mine, nor that of my party," she said.
Scottish Labour leader Kezia Dugdale said: ''Brexit isn't the motivation for another referendum - it's just the latest excuse."