The latest Des Moines Register “Iowa Poll” shows Vice President Al Gore’s lead widening, slightly, over Bill Bradley. Al Gore began Sunday in Clinton, where he met with 150 local democrats and told ’em not to believe the polls and get to over-cofident.Bill Bradley was the last man to leave the trail, with a huge, late-night rally at Drake University.Texas Governor George W. Bush made just two campaign stops yesterday, in Waterloo and Mason City.