WASHINGTON — President Bush's attempt to win $560 million in aid this year to assist Mexico's anti-narcotics efforts has run into a rebellion from some Texas Republicans worried about corruption, inefficiency and now defections among Mexican police officials. Wednesday's disclosure that three Mexican police chiefs are seeking asylum in the United States prompted the Texans to push Thursday for congressional hearings on the bloody border war among Mexico's drug cartels and a reassessment of U.S. anti-drug assistance to the country. "Our first priority must be to secure our own border and equip our own personnel before we even discuss sending...