WASHINGTON (AP) - Call it the law of unintended consequences. A new national backup system meant to ensure that millions of eligible voters are not mistakenly turned away from the polls this year, as happened in 2000, could wind up causing Election Day problems as infamous as Florida's hanging chads. Congress required conditional, or provisional, voting as part of election fixes passed in 2002. For the first time, all states must offer a backup ballot to any voter whose name does not appear on the rolls when the voter comes to the polling place on Nov. 2. If the voter...