The US presidential candidates are heading into the final two days of campaigning with the outcome still too close to call. Republican Mitt Romney will campaign in Iowa, Ohio, Pennsylvania and Virginia, while Barack Obama heads for New Hampshire, Florida, Ohio and Colorado. Both candidates addressed large rallies on Saturday in key swing states. Both Mr Obama and Mr Romney are showing signs of exhaustion as they continue their daily, multiple-state visits to attract any undecided voters in the states that will determine the winner. Mr Obama told the 24,000 people in Bristow, Virginia, that the planning and organization of his campaign now no longer mattered. Mr Romney criticized Mr Obama for saying that voting would be their "best revenge" on the Republicans. “Let me tell you what I'd like to tell you: Vote for love of country. It is time we lead America to a better place." Said Romney Later, in Colorado Springs, the Republican challenger told supporters that Tuesday's election would be "a moment to look into the future, and imagine what we can do to put the past four years behind us". An opinion poll on Sunday for ABC News and the Washington Post put the two candidates at 48%, with even voters who term themselves independents split evenly on 46%. Mr Romney remains favoured in the whites, seniors and evangelical groups; Mr Obama in women, non-whites and young adults. Mr Obama remains slightly ahead in most of the nine-or-so swing states that will determine the election.