Cracks are also forming in the coalition favoring repeal. The Bush plan would phase out the tax over nine years, much like the bill that passed the House and Senate last year with significant Democratic support but was vetoed by President Bill Clinton. But now that there is a president who favors elimination of the tax, some want to snuff out the tax immediately. Others want to repeal it but impose new taxes on the wealthy.

Lawrence B. Lindsey, [Bush]'s chief economic adviser, said the president wants to see his approach adopted but is leaving the structure of the repeal up to Congress. "He has told the leadership, 'You guys make the sausage, I just brought the meat and spice,' " Lindsey said. Lindsey acknowledged that Bush would slowly eliminate the estate tax because otherwise it would bust his budget, and that decision still holds because Bush is firm on keeping the overall cost of the tax cut at $1.6 trillion.

There is considerable uncertainty over how repeal would affect levels of charitable giving. Contributions to charitable and educational institutions are exempt from the estate tax. Some argue that elimination of the tax would encourage fewer people to give large chunks of their estates to nonprofits. A recent study by the Urban Institute estimated that repeal could reduce bequests from 10 to 33 percent.