President Bush signed a bill Thursday authorizing 700 miles of new fencing along the U.S.-Mexico border, hoping to give Republican candidates a pre-election platform for asserting they're tough on illegal immigration. "Unfortunately the United States has not been in complete control of its borders for decades and therefore illegal immigration has been on the rise," Bush said at a signing ceremony. "We have a responsibility to enforce our laws," he said. "We have a responsibility to secure our borders. We take this responsibility serious." He called the fence bill "an important step in our nation's efforts to secure our borders."...