Republican and Democrat leaders ended a last burst of campaigning yesterday as opinion polls gave President George W Bush's party the slimmest of edges in several key Senate contests. Republicans were expected to strengthen their hold on the House of Representatives but Democrats remained confident that they could cling on to the Senate in an astonishingly close contest that could turn on a few thousand votes in a handful of states. Charlie Cook, an independent pollster, said the Senate was going to be "an absolute photo finish" that could rival the 2000 presidential election and added: "I don't know if...