Officials on high alert in Arizona's Maricopa County as they hope to avoid election count disruption

Donald Trump and his allies targeted Arizona's most populous county with fake claims of election fraud in 2020

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Inside a fenced and walled-off security compound at the vote tabulation centre in Phoenix, Maricopa County, local officials emerged hours into election day to celebrate “calm” as Arizona voters cast their ballots.

Maricopa, with a population of 3.9 million, is Arizona's largest county and in 2020 it was targeted by Donald Trump and his supporters as they claimed fraud after Democrat Joe Biden won by just 0.4 percentage points. It has been a hotspot for conspiracy theories since then.

County Sheriff Russ Skinner told reporters that every local security agency remains “dialled up” as election day continues, and so far there have been “no credible threats relative to public safety”.

Fears of, and preparations for, violence are reflected at the national level this election cycle. A Scripps News/Ipsos poll found that 62 per cent of Americans – including 70 per cent of Democrats and 59 per cent of Republicans – say violence related to the election this year is somewhat or very likely.

The FBI warned of bomb threats at polling stations in “multiple” US states on Tuesday, adding that none were credible but many appeared to have originated from Russia. Authorities in the US state of Georgia earlier said bomb threats had briefly disrupted voting in some precincts.

This election cycle has been a volatile one, and security for election day had reached unprecedented levels given concerns over the possibility of civil unrest, election rigging and violence against poll workers.

Maricopa County supervisor Bill Gates said the county had invested millions of dollars into making sure “the workers who are here today feel safe”.

“Things have been very calm,” he added.

The National on Tuesday observed vote counters, operating in shifts, tally ballots with mistaken markings or ink stains to “determine voter intent”. These bipartisan volunteers are brought in by vetted applications, county officials said.

The county did not allow close-up photographs of election workers, in part out of concern for their safety.

In Arizona, the sole swing state of this election to border Mexico, growing anti-immigrant sentiment in the US has played a major role in “setting the stage for election denialism”, immigration advocate Victor Guillen Febres – an immigrant from Venezuela who works with the national group United We Dream – told The National on an early morning canvass.

Mr Trump's powerful allies, like Tesla founder and X chief executive Elon Musk, have claimed Democrats are “importing” immigrants who will vote for them in elections. Others have alleged undocumented migrants have cast ballots without the legal status to do so.

“We have seen this hateful rhetoric really divide and confuse people about our electoral process, but even more importantly it actually leads to real hate and violence in our communities,” said Mr Febres.