President George W. Bush on Thursday announced that U.S. Agriculture Secretary Mike Johanns is resigning and is expected to attempt a run for the U.S. Senate in Nebraska.Bush said Johanns “brought focus and energy to the department” but was “serious about going home and possibly serving the nation in a different capacity.”Deputy Agriculture Secretary Charles Conner will take over as acting secretary, Bush said.Johanns drew immediate criticism for leaving his post before Congress finished work on a new farm bill, a goal he had said he wanted to reach by the end of the year, the Associated Press reported.The legislation contains billions of dollars in aid for farmers and pays for nutrition programs. The current version expires Sept. 30.Former Nebraska congressman Hal Daub (Republican), himself a candidate for the Senate seat, critized Johanns for leaving when he “could have been instrumental in securing the passage of a strong farm bill, legislation that is so desperately needed by our state's farmers, ranchers and agribusiness owners.”The Democratic party in Nebraska also criticized the departure.“Unfortunately, the secretary has turned his back on farmers and ranchers repeatedly, most recently walking away from a critical farm bill,” the party said in a news release.Republican officials in Nebraska said Johanns would announce his Senate bid soon. Vicki Powell, Johanns' campaign manager for his two gubernatorial races, said she expects an announcement “in the near future,” AP reported.