Senator Barack Obama has cast his ballot as US voters head to the polls to elect their next president. Mr Obama went to his local polling station in Chicago with his wife Michelle and daughters Malia and Sasha. At least 130 million Americans are voting to choose a successor to Republican President George W Bush. Voting ends in 48 states in hours and the first polls begin to close in parts of Indiana and Kentucky late Tuesday night. The citizens of Dixville Notch in New Hampshire - historically the first to vote in the election since 1960 - have already cast their ballots. Traditionally a Republican stronghold, the 21 registered voters in the tiny village have opted to support Senator Barack Obama, 47, who would be the first black US president if he is elected. It is the first time Dixville Notch has voted Democrat since 1968. Opinion polls indicate he is running ahead of his rival John McCain in enough states to give him more than the 270 electoral votes he needs to win. A victory for Mr McCain, 72, would make him the oldest president to begin a first term in the White House and make his running mate Sarah Palin the first female US vice president. Mr McCain, an Arizona senator, embraced his role as an underdog and said he is gaining ground on Mr Obama. He was hitting seven states on the last day of campaigning as he tried to pull off the biggest upset in recent political history. In Mexico, Mr McCain said: "The pundits have written us off like they have before. "They may not know it, but the Mac is back. We're gonna win this election." Opinion polls show Mr Obama ahead or even with Mr McCain in at least eight states won by Mr Bush in 2004, including the big prizes of Ohio and Florida. Mr Obama leads comfortably in all of the states won by Democrat John Kerry in 2004. Breakthrough victories in any of those traditionally Republican states - including Virginia, Colorado, Indiana and North Carolina - would almost certainly propel Mr Obama to the White House. It was a bittersweet last campaign day for Mr Obama. He choked up in North Carolina when talking about the death of his grandmother, Madelyn Dunham, who helped raise him. Mr Obama, who learned earlier in the day of his grandmother's death from cancer in Hawaii, called her a "quiet hero."