Polling day has unfolded relatively smoothly across the United States with only scattered disruptions and delays.

Leading into Tuesday, more than 82 million Americans had already cast their ballots in a largely successful early voting period with high turnout despite some hiccups and frustrations in the presidential battleground of Pennsylvania.

And when the final day of voting came, the problems that cropped up were “largely expected routine and planned-for events,” said Cait Conley, senior adviser to the director of the Cybersecurity and Infrastructure Security Agency. She said the agency was not currently tracking any national, significant incidents affecting election security.

An election worker processing postal votes at the Philadelphia Election Warehouse (AP Photo/Matt Slocum)

Issues affecting voters on Tuesday included typical election mishaps, from a worker forgetting a key in Arizona’s largest county to an election judge failing to show up at the polls in Pennsylvania’s Allegheny County. Some precincts around the country faced issues with voter check-in processes and e-pollbooks, causing some delays for voters trying to cast ballots. Some areas had ballot printing mistakes and were printing new ballots and extending voting hours accordingly.

Extreme weather across the middle of the country also caused flooding and some other isolated problems, including knocking out power for at least one Missouri polling place that resorted to a generator to keep voting up and running.

Still, in various states affected by rain, voters enthusiastically huddled under umbrellas as they queued up to cast their ballots, not deterred in a presidential election that many US voters view as crucially important to the future of US democracy.

In the western part of the key swing state of Pennsylvania, a few counties saw reports of issues with tabulator machines that scan and count paper ballots filled in by voters. A Pennsylvania state judge ordered polls to remain open for two extra hours in Cambria County, which voted 68% for former president Donald Trump in 2020. The county sought the extension after a software malfunction affected the ballot-scanning machines, though county officials said no one was turned away from the polls and all ballots would be counted.

In Georgia, another presidential swing state, fewer than a dozen precincts were set to stay open late because of delayed openings or evacuations due to alleged bomb threats that were found to be non-credible, according to secretary of state Brad Raffensperger. That included two precincts in Cobb County, which is north-west of Atlanta. They were staying open until 7.20pm because they opened late due to equipment issues.

An independent observer at the Fulton County Election Hub and Operation Centre in Georgia (AP Photo/John Bazemore)

The FBI on Tuesday afternoon said it was aware of multiple non-credible bomb threats to polling locations in several states and said many of them appeared to originate from Russian email domains.

The massive early voting turnout before Tuesday – slightly more than half the total number of votes in the presidential election four years earlier – was driven partly by Republican voters, who cast early ballots at a higher rate than in recent previous elections after a campaign by Mr Trump and the Republican National Committee to counter the Democrats’ long-standing advantage in the early vote.

The early voting period faced minimal problems, even in western North Carolina, which was hammered last month by Hurricane Helene. State and local election officials, benefiting from changes made by the Republican-controlled legislature, pulled off a herculean effort to ensure residents could cast their ballots as they dealt with power outages, lack of water and washed out roads. That appeared to continue on Tuesday, with the North Carolina Board of Elections reporting no voting issues.

Besides the hurricanes in North Carolina and Florida, the most worrisome disruptions to the election season so far were arson attacks that damaged ballots in two drop boxes near the Oregon-Washington border. Authorities there were still searching for the person responsible.

The absence of any significant, widespread problems has not stopped Mr Trump, the Republican nominee, or the RNC, from making numerous claims of fraud or election interference during the early voting period, a possible prelude to challenges after polling day.

Donald Trump has said he will accept the result of the election ‘if it’s fair’ (Evan Vucci/AP)

Mr Trump on Tuesday suggested he would not challenge the results of the election – as long as it is fair.

“If it’s a fair elections, I’d be the first one to acknowledge” the results, Mr Trump said. It was not clear, hpowever, what he sees as meeting that definition.

He followed that up later, shortly before polls were scheduled to close in Pennsylvania, with a post on his social media platform claiming there was “talk about massive cheating in Philadelphia” and that law enforcement was on the way.

Mr Trump did not provide details, and there was no immediate indication of what he was referring to.

Philadelphia district attorney Larry Krasner issued a statement responding to Mr Trump’s post, saying the only suggestion of cheating was coming from the Republican presidential nominee.

“There is no factual basis whatsoever within law enforcement to support this wild allegation,” Mr Krasner said. “We have invited complaints and allegations of improprieties all day. If Donald J. Trump has any facts to support his wild allegations, we want them now. Right now. We are not holding our breath.”

One of three Philadelphia election board members, Seth Bluestein, a Republican, said on social media there is “absolutely no truth to this allegation. It is yet another example of disinformation.” Voting in the city is “safe and secure,” he said.

A late effort by Republicans to challenge Atlanta-area election offices’ collection of postal ballots last weekend after early voting had ended was rejected as “frivolous” with Trump-appointed US district judge R Stan Baker saying the Republican argument “does not withstand even the most basic level of statutory review and reading comprehension”.

Mr Trump’s Democratic opponent, vice president Kamala Harris, has urged voters not to fall for Mr Trump’s tactic of casting doubt on elections. She was spending Tuesday afternoon turning out her own vote at a phone bank hosted by the Democratic National Committee, and said phone banking represents “the best of who we are”.

This is the first presidential vote since Mr Trump lost to Joe Biden four years ago and began various attempts to circumvent the outcome and remain in power. That climaxed with the violent January 6, 2021, attack on the US Capitol to halt certification of the results after Mr Trump told his supporters to “fight like hell”.

Even now, a solid majority of Republicans believe Mr Trump’s lie that Mr Biden was not legitimately elected, despite reviews, audits and recounts in the battleground states that all affirmed Mr Biden’s win.

Kamala Harris spent Tuesday helping at a phone bank with volunteers (AP Photo/Jacquelyn Martin)

Through four years of election lies and voting-related conspiracy theories, local election officials have faced harassment and even death threats. That has prompted high turnover and led to heightened security for election offices and polling sites that includes panic buttons and bullet-proof glass.

While there have been no major reports of any malicious cyber activity affecting election offices, foreign actors have been active in using fake social media profiles and websites to drum up partisan vitriol and disinformation. In the final weeks, US intelligence officials have attributed to Russia multiple fake videos alleging election fraud in presidential swing states.

On the eve of polling day, officials issued a joint statement with federal law enforcement agencies warning that Russia in particular was ramping up its influence operations, including in ways that could incite violence, and would likely continue those efforts well after the votes had been cast.

Jen Easterly, the nation’s top election security official, urged Americans to rely on state and local election officials for information about elections.

“This is especially important as we are in an election cycle with an unprecedented amount of disinformation, including disinformation being aggressively peddled and amplified by our foreign adversaries at a greater scale than ever before,” she said. “We cannot allow our foreign adversaries to have a vote in our democracy.”