President Bush has named Al Hubbard, a long-time friend and financial backer, as his chief economic adviser.
President Bush is looking to reform social security and the tax code
Mr Hubbard, an Indiana businessman and classmate of Mr Bush's at Harvard Business School, succeeds Stephen Friedman who stepped down last month.
Mr Hubbard will help shape the Bush administration's second term economic policy which is likely to focus on social security and tax reform.
Mr Hubbard previously worked as an aide to former Vice-President Dan Quayle.
Mr Hubbard will fill the dual positions of assistant to the president for economic policy and director of the White House National Economic Council.
He will become President Bush's third top economic aide since 2001.
Lawrence Lindsay was removed following the 2002 mid-term elections and replaced by Mr Friedman, a former co-chairman of Goldman Sachs.
He resigned in December to return to the private sector.
Mr Hubbard will pilot a number of potentially controversial proposals such as plans to redesign the tax code and to allow people to pay social security into private investment accounts.
The latter policy, in particular, is expected to meet opposition in Congress.
Mr Hubbard is no stranger to the White House, having served as an aide to former Vice-President Dan Quayle and executive director of the Council of Competitiveness in the early 1990s.