Barack Obama's prospects for defeating John McCain and becoming the 44th American president may be apparent shortly after the first polls close Tuesday in the eastern United States.
An Obama victory in just one of four key states that voted Republican in 2004 Ohio, Florida, Virginia or North Carolina would leave McCain with almost insurmountable hurdles to winning the race.
The US presidency is decided not by a nationwide popular vote, but by a state-by-state tally of electoral votes. The winner needs at least 270 electoral votes.
Obama is likely to take all the states won by fellow Democrat John Kerry, when he lost to George W Bush in 2004. In addition, he is heavily favored in two states won by Bush: Iowa and New Mexico. That would leave him with 264 votes just six shy. That being the case _ and with the caution that polls have proven faulty many times in the past Obama would only need a victory in any one state from among Ohio, with 20 electoral votes; Virginia, 13; North Carolina, 15; and Florida, 27.
Ohio is particularly critical. The state was the highly contested four years ago, when it put George W Bush back in the White House. Ohioans have not voted for a Democrat since 1964 and no Republican has won the executive mansion without winning the state dating back to Abraham Lincoln in 1860.
Florida, likewise, presents a significant history. As recently as the disputed 2000 contest between Bush and then Vice President Al Gore, the US Supreme Court stepped in to end an extended recount, giving the election to Bush. Gore won the nationwide popular vote. The four states all lie in the US Eastern Time zone, where polls will be closing first. Thus, an Obama victory in any one of them could be a strong predictor of the election's final outcome. For McCain, on the other hand, a victory in all four of those states where the latest Associated Press-GFK survey shows Obama leading or tied still would not get him to 270 electoral votes. The AP poll shows Obama leading McCain by 7 percentage points, 48-41, in Ohio and by a similar margin, 49-42, in Virginia. In Florida and North Carolina, Obama holds 2-point leads, both within the polling margin of error.
The picture could change dramatically if McCain's most recent campaign charge in Pennsylvania has proven fruitful. Were he to win there, he could pick up 21 electors that, combined with those in the other four eastern battleground states, would put him over the 270 mark. Most polls show Obama with a hefty margin in Pennsylvania. All such permutations and combinations depend, of course, on polls proving correct and the absence of hitches in state by state voting.
None of the scenarios depending on the Eastern battleground states take into account once-reliably Republican Indiana, Missouri, Colorado and Nevada, any of which Obama could win. Some polls show Obama with slight leads within the margin of error in both Indiana and Missouri, while other surveys put him significantly ahead in both Nevada and Colorado. None of these four states, however, would come into play unless McCain pulls several upsets beyond Pennsylvania in states that will be closing first in the eastern United States.
Given current polling, and again assuming they are correct, McCain has very few paths open in his bid to gain the White House. That does not foreclose victory but requires an extraordinary flow of votes in his direction in many states now in Democratic column in the final few days before Tuesday's vote.