President Bush announced that Dr. Mark B. McClellan, the food and drug commissioner, will be named to run Medicare and Medicaid, the health insurance programs for more than 70 million Americans. Dr. McClellan, 40, is a graduate of The University of Texas at Austin, the brother of the White House press secretary, Scott McClellan, and a son of the Texas comptroller, Carole Keeton Strayhorn, who has been carrying on a public spat with Governor Perry and has hinted that she might run against Governor Perry in the 2006 Republican Primary.