Although U.S. Senator (Republican - Arizona) John McCain's has been criticized by conservatives in his party for his inconsistent support of President Bush's tax cuts, his recent no-new-taxes pledge and his prior Senate votes on the estate tax seem to indicate that as president he would be likely to preserve the status quo on the estate tax: in 2007, McCain voted to increase the estate tax exemption to $5 million and to reduce the maximum estate tax rate to 35%; and in 2006, McCain voted to permanently repeal the death tax and to make the Bush estate (and income) tax cuts permanent.
Source: OnTheIssues.Org: John McCain on Tax Reform
The conservative Club for Growth, which favor repeal of the estate tax, rated McCain's voting record 76 out of 100 for 2006 for pro-growth economic policies.
Barack Obama, Democrat for President, on the Estate Tax
Hillary Clinton, Democrat for President, on the Estate Tax
John McCain Official Site: McCain Tax Cut Plan
October 2008 update: McCain has clarified that he supports raising the estate tax exemption amount to $10 million for a husband and wife and cutting the tax rate on larger estate to 15 percent. He also supports lowering the federal corpoarte tax rate from 35 to 25 percent.