<p>YORBA LINDA, Calif. (AP) - Former U.S. Treasurer Rosario Marin, one of four Republican candidates challenging Democratic Sen. Barbara Boxer, said Thursday that economic and legal problems in Mexico were primarily to blame for this country's "failed immigration policy."</p>
<p>Marin, a Mexican immigrant, called on leaders of that country to stimulate the economy of Mexico by restructuring its tax system, encouraging private investment and funding $50 billion in repairs to its national power grid.</p>