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.
Zack Stalberg, president of the Committee of Seventy, a Philadelphia-based elections watchdog, said most of the hundreds of calls the group has received so far were about "massive confusion" over voter ID requirements.
But he said only a small percentage of those calls — maybe 10 percent — have been from voters who were either turned away or saw people turned away because they lacked photo ID.
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.
LINES SNAKE AROUND THE BLOCK
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.
"When you look at the lines that have formed in places like Ohio, they are longer than the lines in Baghdad and Kabul," said Wade Henderson, president of the Leadership Conference on Civil and Human Rights.
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.
State elections officials said the issue was moot because supervisors in the three counties in question had opened up on Sunday and Monday to allow voters to cast absentee ballots in person after the official end to early 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.
PROBLEMS FOR COLLEGE STUDENTS
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.
"Right now, it's annoying me," said Kristen Wiley, 20, a junior from Boca Raton who said she had requested, but not received, an absentee ballot from Palm Beach County. She was waiting in line for a provisional ballot, knowing it would not count unless her eligibility is later verified.
"If it's close enough, they'll count it. Right now it seems everything is close," Wiley said. She declined to say who she planned to vote for.
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.
Last Friday Ohio's Republican Secretary of State Jon Husted issued a controversial directive that ordered county boards of elections to reject provisional ballots when every part of the form was not properly filled out. Voting rights groups and unions have protested and sued in court.
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."
He said the patches did not change any county's tabulation system or voting machines. "We provided these counties a separate reporting tool. All it does is, it takes the report generated by their tabulation system, and puts it in the tool that formats it so it can be directly uploaded on our website," McClellan said in a phone interview.