WASHINGTON (Agencies) - The two men seeking to become president of the United States of America are beginning one final weekend of campaigning before election day. Democratic candidate Barack Obama still holds a poll lead, but one new survey suggests his lead over Republican John McCain is narrowing slightly. McCain holds rallies in Virginia and Pennsylvania before appearing on TV show Saturday Night Live. Obama campaigns in Nevada, Colorado and bellwether state Missouri. Both men are visiting states seen as crucial to their chances of winning Tuesday's election. Analysts say McCain needs to win in Pennsylvania - where he is behind in state polls - to have a chance. Polls in Virginia, which voted Republican in 2004, show Obama has pulled ahead of his rival there. Obama also leads McCain in Nevada and Colorado, both of which voted for George W Bush four years ago. Missouri is seen as a vital state to win because of its record of backing the eventual winner in almost every election since 1904. Obama leads in Missouri by a very narrow margin, polls show. Obama is extending his campaign advertising into traditionally Republican territory over the weekend, running advertisements in Arizona, his rival's home state, as well as Georgia and North Dakota. Polling officials are expecting some 130 million Americans to vote - a turnout which would prove higher than in any election since 1960. Security is of most concern in Chicago, Obama's base, where up to one million people are expected to turn out in the city centre for what they hope will be a White House victory for the Illinois senator. But McCain is remaining defiant, playing on his status as the underdog and telling supporters on Friday night that he would still make a late run to victory. He was boosted by the support of California Governor Arnold Schwarzenegger, who gave a rousing speech in the swing state of Ohio. The ex-film star said McCain was a real 'action hero' who had spent more time as a prisoner of war than Barack Obama had served in the US Senate. "We're closing, my friends, and we're going to win in Ohio," McCain told the Ohio crowd. "We're a few points down but we're coming back and we're coming back strong." In a new poll Reuters/Zogby poll released on Saturday Obama's lead was down to 5 per cent, at 49 per cent to McCain's 45 per cent. The gap narrowed from 7 per cent in the previous survey. Obama warned supporters to expect a hard fight until the very end of the campaign. "We are four days away from changing the United States of America," he said.