After all, this is what Brown regards as The Great Dividing Line: the Tories implementing a tax cut for their "rich friends," on the one side, and Labour implementing policies "for the many," on the other. Darling's decision to raise the IHT threshold to £350,000 for single people and £700,000 for married couples undermined that crude message. Reversing the policy may, in Labour strategists' eyes, strengthen the dividing line.
If so, it looks like the Pre-Budget Report debate, as well as the election campaign, will produce even more of the same anti-"toff" rhetoric on Labour's part.
But the question now is how the Tories would respond. As it happens, their position on the IHT cut already seems to have weakened. Before the summer recess, there were rumblings that the measure had been "shelved" and, in his conference speech, George Osborne would only say that it will be introduced in the first Parliament of a Tory government. But you wonder whether Cameron & Co. will now develop that position as Labour turn, ever more, to bar-brawling tactics.
UPDATE: Danny Finkelstein has some useful extra thoughts on this here.