Anyone still need a reason to abandon "grand bargains" and deals negotiated between this President and GOP Congressional leaders? Here it is: The revival of two dormant provisions of the tax code means the much ballyhooed $450,000 income threshold for the highest tax rate is largely fake.

The two provisions are the infamous PEP and Pease, which aficionados of stealth tax increases will recognize immediately as relics of the 1990 tax increase. Those measures, which limit deductions and exemptions for higher-income taxpayers, expired in 2010. The Obama tax bill revived them this week. It isn't going to be pretty.

Under the new law, some of the steepest tax increases may fall on upper-middle class earners with incomes just above $250,000. Here's why:

During the negotiations, the White House won a concession from Republicans to allow phaseouts for personal exemptions and limitations on itemized deductions, starting at an income of $250,000 for individuals and $300,000 for joint filers.

The Senate Finance Committee informs us that in effect the loss of the personal exemptions, currently $3,800 per family member, can mean a 4.4 percentage point rise in the marginal tax rate for a married couple with two kids and incomes above $250,000. A family with four kids in that income range faces about a six percentage point marginal rate hike. The restored limitations on itemized deductions can raise the tax rate by another one percentage point.