Polls have closed in the US midterm elections, with American voters turning out in droves to have their say on the economy, abortion rights, and the future of President Joe Biden's agenda. 

What was expected to be a red tsunami — wiping out Democrats in the House of Representatives and the Senate — is looking more like choppy seas for the incumbent party, which was hoping to hold on to its razor-thin majorities. 

By the end of election night, Republicans were on track to take back control of the house, but Democrats held on to several competitive districts, avoiding the bloodbath pundits and polls had predicted. 

Closely watched swing states such as Georgia, Arizona and Nevada, which may decide the balance of the Senate, could still take several days to finalise their counts. 

In Pennsylvania, Democrat John Fetterman finished the night by claiming victory over his Republican rival Mehmet Oz, a celebrity doctor recently disavowed by Oprah Winfrey. 

Meanwhile in Georgia, Democratic Senator Raphael Warnock and his Trump-backed challenger, former football star Herschel Walker, are likely headed for a run-off if neither can secure 50 per cent of the vote. 

Each state has its own rules for when and how votes are counted, which means it could take several days until the national picture comes into focus. 

Here's what we know so far. 

The first sign that the Republican wave wouldn't come? Virginia

Before election day, the state of Virginia was described as the "canary in the coal mine" for early clues on how the midterms might play out for Democrats. 

On America's east coast, the state is one of the first to start counting votes. 

Democratic representative Elaine Luria, who rose to national prominence on the January 6 committee, lost to state senator Jen Kiggans by around four percentage points. 

Luria's fate, which may have been sealed by an unfavourable redistricting, was flagged as a test for her party and the popularity of the high-profile committee tasked with investigating the insurrection.

By comparison, representative Abigail Spanberger, who is also a Democrat, fended off a challenge from Republican Yesli Vega in another battleground seat. 

If she lost, the New York Times had predicted Republicans would likely go pick up 20 seats or more. 

A loss by Democratic representative Jennifer Wexton — who represents the left-leaning Northern Virginia suburbs of Washington DC — would have been a death knell for the Democrats. 

But she held on, defeating Republican Hung Cao. 

The mixed results gave the party hope that all was not lost. 

Inflation and abortion appeared to be the dominant issues 

Polls suggested Americans' main concerns were the economy, abortion rights, crime and immigration. 

Like many countries around the world, the US is struggling to rein in inflation, which is stuck close to a 40-year high at 8.2 per cent. 

As a result, the US Federal Reserve has raised interest rates, making mortgages, credit cards and loans more expensive.

The Republican party ran its campaign hard on the health of the economy, placing the blame squarely on President Biden. 

Last month, 32 per cent of pro-Republican campaign ads focused on inflation, compared to just 8 per cent of pro-Democrat ones, according to an analysis by the Wesleyan Media Project.

Exit polls suggest the strategy paid off, with 44 per cent of Republican voters naming inflation as their biggest worry.

Meanwhile, Democrats named abortion access as their biggest motivator, according to exit polls. 

Earlier this year, America's highest court overturned the constitutional right to an abortion and sent the issue back to the states. 

Thirteen American states have since banned most abortions. 

Democrats had hoped the issue would drive outraged voters to the polls in huge numbers. 

It will probably take a couple of days to delve into the data and figure out how much abortion played into the race. 

But 46 per cent of women nationwide said they were angry about the change to abortion rights, while another 20 per cent said they were "dissatisfied", according to NBC's exit poll.

Ultimately it might not be quite enough for Democrats to keep control of the House of Representatives. 

But control of the Senate — something several forecasting models predicted would fall to Republicans — is now a toss-up. 

Election deniers cried foul in Arizona

A legal stoush is already brewing in Arizona, which became ground zero for election denialism in the wake of the 2020 election.

Just hours after polls opened, Maricopa County — the state's most populous — reported technical issues with automatic vote-counting machines at around 60 polling locations. 

Maricopa County Recorder Stephen Richer called the malfunctions "disappointing" and sought to reassure voters their ballots would be counted. 

But the delays were quickly seized on by some Republicans, including Trump-backed gubernatorial candidate Kari Lake and the former president himself. 

"Can this possibly be true when a vast majority of Republicans waited for today to vote?" Trump wrote on Truth Social. 

"Here we go again? The people will not stand for it!!!" 

Poll workers tried to allay the concerns of frustrated voters in line, as conspiracies theories began to swirl online, fuelling baseless claims of fraud. 

"No one's trying to deceive anybody," one poll worker says in a video circulated on Twitter. 

The county later attributed the source of the glitch to a printing problem, solved by changing the printer settings. 

"It appears some of the printers were not producing dark enough timing marks on the ballots," county officials said in a statement. 

"This solution has worked at 17 locations, and technicians deployed throughout the county are working to resolve this issue at the remaining locations." 

Even so, in a sign of what may be to come, Republican National Committee and several Republican candidates filed an emergency lawsuit calling for polls to remain open longer.