President Bush has announced the resignation of Agriculture Secretary Mike Johanns.
At the White House Thursday, the president thanked Johanns for his service to the department.
Johanns, a Republican, is expected to run for the U.S. Senate from Nebraska.
The resignation follows Republican Senator Chuck Hagel's announcement last week that he is retiring from the U.S. Senate. Hagel, who has been a vocal critic of the Iraq war, has served as a senator from Nebraska since 1996.
Johanns is the latest Bush administration official to leave his post. Other recent departures include former Attorney General Alberto Gonzales and Mr. Bush's longtime political adviser, Karl Rove.