1996. The Conservative Party has clear personal divisions and plently of overambition mixed with incompetence today, but they are not as hopelessly divided as they were back in the 90's with Europe. During the 1997 campaign Major had to beg his MPs "not to bind his hands" and scores of them introduced personal manifestos setting our their own views. That made it impossible to take them seriously, amplifying the effect of Black Wednesday and the endless scandals that destroyed the government's reputation. The opposition was also not just competently run, it also inspired hope and symbolized a breath of fresh air.
Bad as it is right now - and I firmly believe they're headed for a rightly deserved thumping -, there are some silver linings. Even amidst the predictions of wipeout, the party will still be left in a stronger position in Scotland than the 1997 void for example, the electorate has proved that it is quite capable of swinging strongly against incumbents (as opposed to it taking three painful elections before the Tories could barely get rid of Labour), Europe is no longer there to split the party apart, and Starmer, while unfairly maligned, is no Tony Blair.
Scotland reflexively votes the reverse of England and Wales lately, so Conservatives loosing all their seats except their Scottish ones would be fun.
The economy is the single factor, if it's not fixed in time then out they go.