I know that this would be a title with a lot of contenders, but let's look at the evidence. It's not because he's for a death tax: that's just ordinary tone-deafness, coupled with the standard Democratic politician's assumption that it was all really their money all along, and they were just letting individual citizens hold on to it for a while. It's not even that Congressman Sherman is demanding, in exchange for his vote, that the negotiated rate of 35% over 5 million (far too high, by the way) be retroactively applied to 2010.
It's that the man apparently expects anybody sane to take him up on his offer. The Politico article delicately put the likelihood that Republicans would agree to this as being 'questionable;' the actual response from the GOP would be far earthier, and a good deal more direct. You might remember that in 2009 a trial balloon was floated to keep the 2010 death tax at 45% over 3.5 million; it got shot down in the Senate. The current number essentially duplicates the 2009 death tax rate, and echos a compromise put together by Senators Kyl and Lincoln earlier in the year; and if the tax compromise doesn't pass the rate goes to 55% over 1 million in January. The White House does not want to explain that to the American people. Brad Sherman, on the other hand, is a five-term Congressman from a double-digit partisan district, which means that he was about due to start Embracing The Crazy anyway*. So, probably no real surprises here.
Moe Lane (crosspost)
*I'm not the sort who will give a Troofer like Alex Jones traffic, but here's a link to the search results that'll show the Congressman appearing on Jones' show to explain away his Embrace Of The Crazy... which pretty much tells you everything that you need to know, right there.