Millions of Americans are flocking, in what appears to be record numbers, to the polling booths, to vote for a successor to George W. Bush.
Democrat Barack Obama holds a decisive edge in the opinion polls but his opponent, Republican John McCain, defiantly believes he can still win the race to the White House.
A victory for McCain, at the age of 72, would make him the oldest president to begin a first term.
Victory for Obama would make him the first black US president.
Twenty nine million Americans voted early in this long and bitter struggle. In all, 130 million American citizens are expected to cast their votes in a higher turn out than in any election since 1960.