Americans began voting in a historic Presidential poll on Tuesday with Democrat frontrunner Barack Obama [Images] bidding to become the first black occupant of the White House and his Republican opponent John McCain [Images] hoping for a surprise election-day upset amid a raft of opinion surveys.

With Democrats eyeing both the Senate and House of Representatives, Tuesday's polls may also result in a political re-alignment on the Capitol Hill.

The 47-year-old first-time Illinois Senator Obama, who clinched the Democratic Presidential nomination after a long hard-fought battle with seasoned Hillary Clinton [Images], is widely expected to emerge victorious with a number of opinion polls giving him an edge over the Vietnam War veteran McCain.

But, the 72-year-old McCain, seeking to leave behind the legacy of incumbent George W Bush [Images] who is being criticised for his foreign and economic policies, hopes to make a remarkable comeback in the race for Presidency defying poll pundits. If he wins he will be the oldest person to be inaugurated as President.

Some states, including Florida [Images], Georgia and Colorado started early voting with a large number of people queueing up to cast their ballots.

"Today is Election Day. The opportunity to set our country on a new path has never felt more real than it does right now. The polls are open in most places, and people are already making their voices heard for change. There's just one thing left to do -- vote and make sure everyone you know votes, too," Obama said in an e-mail message to his supporters.

Obama opened his account with a landslide win in Dixville Notch, an isolated village in New Hampshire's northeast corner which voted shortly after midnight Monday night and drew the media attention for being the first place in the country to make its presidential preferences known.

It was the first time since 1968 that the village leaned Democratic with Obama winning 15 of 21 votes cast in a polling that saw a full 100 per cent registered voters participating.

However, CNN said the result in Dixville Notch is hardly a reliable bellwether for the eventual winner of the White House -- or even the result statewide.

McCain, true to his word, has not given up insisting that America is in for a rare come from behind win.

On election day, the subdued analysis is that this election is one of historic proportions for there is not only the strong likelihood of a young African-American occupying the Oval Office on January 20, 2009 but also that the Democrats are looking to occupy both ends of Pennsylvania Avenue by virtue of controlling the White House and Congress.

The polls' outcome is expected to have definite implications domestically and globally, including on South Asia and India-United States relations.

For Obama, the final stages of his hectic 21-month campaigning had only one sad moment towards the very end -- the passing of his maternal grandmother on Sunday night who had a "meaningful and enduring" impact in shaping his life.

As Americans are looking up to which of the two candidates crosses the 270 Electoral College vote mark, the networks are letting Americans know that they may not be as restrained as was thought and that some of them may not be in the mood to wait for polls in the West Coast to close before making a clear and definite projection if one was available.