U.S. Customs and Border Protection Commissioner Robert C. Bonner and White House Homeland Security Adviser Frances Fragos Townsend appear to be at the top of a shortlist of candidates to head the Department of Homeland Security, as the White House seeks to rebound after the unexpected withdrawal of former New York Police Commissioner Bernard Kerik. Another candidate is Asa Hutchinson, the department's undersecretary for border and transportation security, administration and law-enforcement sources said. Mr. Hutchinson reportedly has lobbied for the post. Some Republicans, including Sens. John McCain of Arizona and Senate Governmental Affairs Committee Chairman Susan Collins of Maine, also...