NEW YORK - From makeshift sites in the US East Coast communities hit by the hurricane Sandy to more typical booths in schools, Americans cast their ballots on Tuesday for the presidential slot, with Democratic incumbent Barack Obama having a slight edge over his Republican challenger Mitt Romney.

All sides are waiting, in particular, a verdict from the nine battleground states whose votes will determine which man can bag the 270 electoral votes needed for victory.

Sporadic complaints about voting procedures surfaced from Pennsylvania to Florida, while long lines in many states posed their own challenges in what could be one of the closest presidential elections in US history.

It was unclear what impact controversies over everything from the presence of poll watchers to software installation on tabulation machines would eventually have on an election that caps the long and bitter presidential campaign. National opinion polls showed President Barack Obama and Republican challenger Mitt Romney in a virtual dead heat.

Watchdog groups said there was confusion over voter ID requirements in Pennsylvania, a state Obama had been expected to win, but that Romney visited in recent days as he sought to expand the battleground.

“Poll workers have been poorly and wrongfully trained, and they are standing there and sitting there and requiring people to show ID, and sending people home if they don’t have the ID,” said Barbara Arnwine, executive director of the Lawyers’ Committee for Civil Rights, at a press conference in Washington. “The state of Pennsylvania ought to be ashamed.”

A judge in Pennsylvania last month blocked the state from requiring voters to show photo identification, a setback for Republican state officials who had championed the law.

Pennsylvania’s ID rules were among a raft of new voting laws passed mostly by Republican-led legislatures in dozens of states since 2011. The courts have thrown out the harshest of the new laws, or at least ordered their implementation delayed.

Republicans had their own complaints in Pennsylvania. The party got a court order to reinstate 75 Republican election officials in Philadelphia who allegedly were prohibited from entering polling places.

“This was a shameless attempt from the Obama campaign to suppress our legally appointed Republican poll watchers in Philadelphia and they got caught,” said Pennsylvania Republican Party Chairman Rob Gleason.

Long lines at polls in many states prompted concerns that some voters would give up without casting their ballots. Lengthy waits to vote were reported in Florida, Virginia and Ohio, all key swing states, as well as New Jersey and New York, states walloped a week ago by superstorm Sandy.

Civil rights leaders said the lines threatened to be an international embarrassment for the United States.

In the densely populated Miami area, wait times on Tuesday ranged from 15 minutes to more than three hours to vote a lengthy ballot. A lawsuit had been filed already on Sunday in Florida over the waiting times for early voting, which in some cases on Saturday stretched to six and seven hours.

The suit, filed by the state’s Democratic Party, said lines in Democratic-leaning areas of Miami, Broward and Palm Beach counties were longer than in others, deterring or preventing people from voting.

Some Florida ballots were up to 12 pages long. Among other things voters were considering 11 proposed amendments to the state constitution, including one to stop implementation of President Obama’s signature health care plan.

Florida Secretary of State Ken Detzner said that the hotly contested state, which has 11.9 million people registered to vote, could be in for a record turnout.

College students voting away from home also ran into problems in Florida.

At the massive University of Central Florida in Orlando, with some 58,000 students, many students had to use provisional ballots because their voter registration cards list their home addresses. A new state law for the first time prohibits making address changes on the spot.

Another twist in Florida were the hundreds of voters in Clearwater who received automated telephone calls telling them they had until the end of “tomorrow” to vote. The Tampa Bay Times quoted a local election supervisor saying that the calls were supposed to have gone out on Monday.

Multiple problems were reported in New Jersey, where superstorm Sandy crashed ashore eight days ago.

“There’s just one word to describe the experience in New Jersey, and that is a catastrophe,” Arnwine told reporters.

She said that computer servers have crashed; voters were being asked for ID that is not required; some polling places opened late; and multiple locations did not have ballots.

While Obama was expected to win easily in New York, New Jersey and Connecticut, the states most affected by Sandy, a low turnout there could expose fissures in the arcane Electoral College system that decides the presidency.

With the race in a dead heat, according to most polls, it’s possible that low voter turnout in storm-ravaged states could allow one candidate to win the state-by-state Electoral College race while losing the popular vote.

In battleground state Ohio, there was nervousness about the role that provisional ballots could play. If Ohio voters earlier requested an absentee ballot but then decide to vote in person, they are required to cast a provisional ballot.

But under state law provisional ballots cannot be counted until 10 days after the election, a spokesman for the Ohio secretary of state said.

Former Ohio Governor Ted Strickland, a Democrat, told CNN that counting those ballots could delay the result.

There is also a lawsuit over software patches installed at the last minute on electronic vote tabulation systems in some Ohio counties. Matthew McClellan, spokesman for the secretary of state’s office, said the concerns were “ridiculous.”

In addition to the president, the voters cast ballots for the members of the House of Representatives and one-thirds of the Senate as well as governors of 11 states. More than 238 million people were eligible to vote, but only 178 million or 75 per cent were registered to vote.

Poll results released over the past few days showed an extremely tight presidential race, prompting analysts to predict that the outcome might not be known until the early morning hours on Wednesday (today).

Obama wrapped up his campaign on Monday in Iowa while Romney held election-day rallies in the battleground states of Ohio and Pennsylvania which could determine who would end up in the White House.

Romney and his wife, Ann, voted Tuesday morning in the Boston suburb of Belmont where the couple lives. Obama cast his ballot during the early voting period in Chicago on October 25.

Voters in the hamlet of Dixville notch, New Hampshire, were the first to cast ballots in the country, with Obama and Romney ending up tied at 5-5. This was the first time that a presidential election ended up tied in Dixville notch which began its tradition of casting the first votes in 1960, an election official said.

More than 31 million Americans cast ballots at early voting sites or by mail in 34 states and the district of Columbia.

While Romney campaigned even on the polling day, Obama opted to make a dozen radio and satellite TV interviews from his hometown of Chicago to keep his closing arguments fresh in the voters’ minds.

“I feel optimistic but only cautiously optimistic because until people actually show up at the polls and cast their ballot, the rest of this stuff is all just speculation,” Obama said in a Steve Harvey Morning Show.

Vice President Joe Biden and his wife, Jill Biden, were among the first voters Tuesday at a polling place in Greenville, Delaware, their home state. Smiling broadly, Biden waited in line with the other voters and greeted them with a handshake.

Romney argued that Obama had his chance and blew it. “The president thinks more government is the answer,” he said in Sanford, Florida. “No, Mr President, more jobs, that’s the answer for America.”

The two candidates and their running mates, propelled by adrenalin, throat lozenges and a determination to look back with no regrets, stormed through eight battleground states and logged more than 6,000 flight miles Monday on their final full day of campaigning, a political marathon featuring urgency, humour and celebrity.

In Washington metro area where temperature plunged below freezing point people were seen enthusiastically lining up to vote across DC, Maryland and Virginia. In New York and New Jersey, battered by the historic Sandy storm, people were seen lining up outside main polling stations. In New Jersey, voters displaced by the massive disaster were allowed to cast mail-in ballots by fax or e-mail, something which raised concerns about possible hacking and fraud.

The New York and Washington metro areas are a home to an estimated 300,000 Pakistani-Americans and a large population of other South Asian voters. Like the rest of America, they are also divided over the choice of president.