WASHINGTON (CNN) - Mitch Daniels, the director of the White House Office of Management and Budget, told the Bush administration Tuesday he will resign, marking the latest exit by one of President Bush's economic advisers.

Daniels' departure follows the resignation earlier this year of Glenn Hubbard, chairman of the White House Council of Economic Advisers. In December, Bush pushed out Treasury Secretary Paul O'Neill, White House economic aide Lawrence Lindsey, and Securities and Exchange Commission Chairman Harvey Pitt.

Daniels' resignation is effective in 30 days.

"Mitch Daniels did this morning inform the president that he will be leaving the White House in 30 days. The president tremendously appreciates Mitch's service to the nation," White House spokesman Ari Fleischer said. Fleischer added that it was too soon to speculate about a successor.

No reason for the departure was given, but administration officials have said Daniels was considering running for governor in Indiana.

As budget director, Daniels prepared President Bush's budget requests to Congress and made projections about federal budget deficits and surpluses, and he also has spoken on behalf of the president's tax-cut plans.

Mitch Daniels, director of the White House Office of Management and Budget.

Not including war costs, Daniels recently projected deficits of $304 billion and $307 billion in 2003 and 2004, respectively -- the highest deficits, in terms of dollar amount, in U.S. history.

When Bush campaigned for a $1.35 trillion tax cut in early 2001, federal budget surpluses were expected to total some $5.6 trillion in the following 10 years. A recent study by the non-partisan Congressional Budget Office projected President Bush's latest tax-cut plan would trigger total deficits in 2004-to-2013 of some $1.8 trillion.

Daniels, in supporting the president's tax plans, has downplayed their budgetary impact, saying rising deficits are due mostly to recession and war. Democrats and other skeptics of the tax cuts have charged that the tax plans have helped erase the once-projected budget surplus.

Congress will likely trim Bush's tax plan to $550 billion at most, mainly due to concerns about the swelling deficit.

Daniels was an executive at Indianapolis pharmaceutical company Eli Lilly (LLY: Research, Estimates) from 1997 to 2001.