As voters flooded polling places across the country on Election Day, some reported problems such as long lines, confusion and voter intimidation in states ranging from Texas to Pennsylvania.

While voting appeared to proceed without headaches in many locations, election observers said they expect a significant increase in the number of issues reported nationwide.

In the first high-profile legal action of the day, Donald Trump’s campaign headed to court for a hearing in Nevada after filing a lawsuit arguing that polls were improperly kept open late during early voting in Clark County.

According to the lawsuit filed by the Republican nominee, this was done “to help Hillary Clinton,” Trump’s Democratic opponent. Trump’s campaign says the voting machines and ballots involved “must be set aside, sequestered and impounded” to preserve the status quo “in the event of post-election challenges.” In a statement, Clark County officials note that the lawsuit asks them to preserve early voting records, something that “is required by state law, and so it is something we are already doing.”

At a hearing Tuesday morning, a skeptical judge questioned the Trump campaign’s attorney and denied the request to preserve evidence in the case.

This lawsuit follows a raft of recent legal wrangling in the days leading up to the election. As the bitter presidential campaign rumbled toward its conclusion, officials across the country have been bracing for the possibility of confusion and chaos on Election Day, owing to a flurry of new voting restrictions and Trump’s calls for his supporters to closely monitor polling places.

Voters in Florida, a key battleground, have reported multiple accounts of voters saying they have encountered aggressive, intimidating behavior, according to a nonpartisan group monitoring election issues nationwide.

“In Florida we continue to receive a substantial amount of complaints about voter intimidation,” said Kristen Clarke, president of the Lawyers’ Committee for Civil Rights Under Law, which is running an independent effort to field voter complaints and questions.

Clarke said her group received reports from Miami-Dade County of “yelling, people using megaphones aggressively.” In Jacksonville, in the northeast corner of the state, Clarke said, “an unauthorized individual was found inside a polling place.”

This person was at St. Paul’s Methodist Church, a polling precinct in what Clarke described as a part of Jacksonville with predominantly black residents.

“He was asked to leave and refused,” she said. “Through our intervention and calls, that individual has been removed. Unauthorized individuals have no place in the polls.”

During early voting, Clarke’s group also received reports from Hollywood, Fla., about “aggressive individuals hovering around individuals as they approach the polling site,” she said during a briefing with reporters. “Some have turned away because they did not feel able to freely cast a ballot.”

Clarke said her group has received reports from about 80,000 voters since the beginning of early voting and expects that figure to reach 175,000 reports by the time the polls close. In 2012, the group received 90,000 calls total on Election Day.

During a telephone interview Tuesday on Fox News, Trump did not say whether he was expecting to argue with the outcome of the election, but he said he believed there were reports of voter fraud happening across the country.

“It’s happening at various places today, it’s been reported,” he said. “The machines, you put down a Republican and it registers as a Democrat, and they’ve had a lot of complaints about that today.”

It was not immediately clear what accounts Trump was referring to when he mentioned “a lot of complaints” about the issue. A report out of Clinton Township, an area near Pittsburgh, quoted some voters saying their tickets were switching from Trump to Clinton. According to that report, officials there said the machines were fixed and the problem resolved.

There have been other issues with machines, including some cases of them showing incorrect votes, though it was unclear how widespread this was.

Wendy Weiser, director of the Democracy Program at the Brennan Center for Justice at New York University School of Law, said that they are seeing more problems with voting machines than they have seen in past election years.

“There are more machine breakdowns and more malfunctions all over the place,” Weiser said. “It’s really widespread.”

These breakdowns are not a surprise, Weiser said, because 42 states are using machines that are 10 or more years old. There have been issues with machines in South Carolina, New York, Missouri, Georgia, Virginia, Pennsylvania, Kentucky, Connecticut, Massachusetts, Chicago and Indiana.

“These machines are just degrading,” Weiser said.

One specific problem has been “vote slipping,” which is what Trump seemed to be referencing and occurs when a voter presses a button on a touch screen for one person but the machine shows them voting for another candidate.

“We’ve seen more malfunctions and more vote slipping all over the place,” Weiser said. But it was not clear how many machines were seeing vote slipping.

Issues with machines caused lines earlier Tuesday at precincts in Virginia, Clarke’s group said. Her group also heard similar complaints from Philadelphia, one of the cities specifically cited by Trump during speeches in which he claimed that voter fraud is “all too common” and asked his supporters to closely monitor other voters.

The office of Philadelphia District Attorney R. Seth Williams said it has assembled a task force including more than 70 prosecutors and dozens of detectives to tackle complaints of voter fraud, intimidation and electioneering.

“We, as expected, had kind of a busy call volume in the morning,” Cameron L. Kline, a spokesman for Williams, said Tuesday morning in a telephone interview. Kline said the task force was not seeing an unusual volume of calls or complaints. “So far the trend is historically rolling the right way.”

The Philadelphia Republican Party posted on Twitter that poll workers in the northern part of the city were handing out literature supporting Hillary Clinton, the Democratic nominee, while inside a polling station.

Problems with machines also cropped up in North Carolina, another major battleground state and home to one of the country’s most high-profile laws imposing new voting restrictions.

There were also other complaints reported across the country. In complaints submitted to The Washington Post, voters described confusion over identification requirements in Pennsylvania, Texas and D.C., among other issues.

Clarke said the lawyers’ committee was contacted about sites that did not open on time in Brooklyn and Boston, along with long lines and broken machines elsewhere.

She said that there were also complaints Tuesday about electronic machines down in Durham County, N.C., which has more than a quarter-million residents outside Raleigh. In Georgia, Clarke said, people complained of “11th-hour polling place changes with no notice issued to voters,” creating uncertainty over where to go.

Leading up to Election Day, there have been some heated confrontations between supporters of Clinton and Trump. The specter of possible violence has loomed over Election Day after a particularly vitriolic campaign, one in which issues of race, class, gender and ethnicity have taken center stage in caustic ways.

In a poll last month, half of likely voters said they were worried about violence on Election Day. Meanwhile, U.S. officials recently said they were investigating a possible threat from al-Qaeda to carry out pre-election terrorist attacks, although authorities described the threat as vague and said they were unclear whether it was credible.

Law enforcement officials from Nevada to Georgia have pledged an increase in officers at some locations, with agencies vowing vigilance and saying they are prepared for possible issues.

The Las Vegas police said units would visit polling locations, though the department noted that early voting in Clark County came and went without any issues of violence at the polls. In Chicago, another city named by Trump when he exhorted his supporters to monitor polling locations, police say it is normal procedure for them to have extra officers visiting these sites to ensure safety.

Police in New York are preparing for “a very unique set of challenges,” because both Clinton and Trump plan to hold election-night events in Manhattan, said James O’Neill, the police commissioner.

But O’Neill said police are prepared to secure more than 1,000 polling locations across the city, as well as the Clinton and Trump events just two miles apart later on Tuesday night.

“Planning for security events like this is a big part of what we do,” O’Neill said during a briefing Monday. “This is nothing new to us.”

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The Washington Post’s Sari Horwitz contributed to this report.