Now, if Labour "needed" the SNP for the numbers, if they were clever, they could surely call their bluff and dare the SNP to vote them out, basically throwing the Tories a chance to form a new government.
That could be a brilliant move. You could legitimately blame the SNP for a Tory entering 10 Downing Street.
But not everyone could be convinced. Whether it is wise playing their bluff depends on what the cause of disagreement is.
Guys you're basically describing how Margaret Thatcher first became Prime Minister