CARLSBAD, Calif. (AP) - Republican presidential candidate John McCain is challenging critics of a proposed immigration overhaul plan to provide a better alternative. The Arizona senator criticized his leading rivals, former Massachusetts Governor Mitt Romney and former New York Mayor Rudy Giuliani, when a reporter asked him about their opposition to a Senate compromise brokered earlier this month. McCain says anyone who doesn't like the plan should offer their own idea. The plan before Congress includes tougher security, guest workers and a path to citizenship for millions of illegal immigrants. McCain says the US can't afford to continue to allow...