Joe Biden on the verge of US presidential victory as counting presses on

The nail-biting US election is on the cusp of finally producing a winner, with Democrat Joe Biden solidifying his lead over President Donald Trump and the decisive state of Pennsylvania set to release results.

Two days after the most tense election in decades, the meticulous vote counting process – complicated this year by a flood of mail-in ballots due to the coronavirus crisis – reached the end game.

Biden, 77, was just one or at most two battleground states away from securing the majority to take the White House. Trump, 74, needed an increasingly unlikely combination of wins in multiple states to stay in power.

The Republican, who shocked the world when he won the presidency in 2016 in his first ever run for public office, spent another day lashing out at the election, claiming fraud and demanding a halt to vote counting.

"IF YOU COUNT THE LEGAL VOTES, I EASILY WIN THE ELECTION!" he claimed in a statement sent out by his campaign, accompanied by no evidence. "IF YOU COUNT THE ILLEGAL AND LATE VOTES, THEY CAN STEAL THE ELECTION FROM US!"

Biden, who has promised to heal a country bruised by Trump's extraordinarily polarising four years in power, maintained his characteristic message of calm.

"Be patient, folks. Votes are being counted, and we feel good about where we are," he tweeted.

All about Pennsylvania?

In Georgia, a generally Republican state, Trump had a razor thin and steadily slipping lead of less than 13,000. With 98 percent of ballots already counted, the president and Biden were headed to a photo finish.

In Arizona and Nevada, Biden held on to slim leads. If Biden wins both those states he would also win the presidency.

But the biggest piece of the puzzle is Pennsylvania, where Trump's early lead is again steadily draining away, as election officials homed in on processing mail-in ballots, which are more typically cast by Biden supporters.

The Democratic hopeful currently has 253 of the 538 electoral votes divvied up between the country's 50 states – and 264 with the inclusion of Arizona, which Fox News and the Associated Press have called in his favour.

If Biden takes Pennsylvania, he'd grab 20 more electoral votes – which would instantly take him over the top of the 270 needed for overall victory.

READ MORE: Is the pandemic the most crucial swing state in the elections?

Trump lashes out

Trump's campaign continued to insist that the president has a way to win, citing pockets of Republican support yet to be counted in such close races.

But Trump's overwhelming focus was on claiming, without evidence, that he was a victim of mass fraud.

Trump prematurely declared victory on Wednesday and threatened to seek Supreme Court intervention to stop vote-counting but it has continued nonetheless.

Since then, his team fanned out across the battleground states challenging the results in court and staging a series of press conferences where supporters lodged allegations of irregularities.

"STOP THE COUNT!" Trump tweeted on Thursday, referring to his claim that the mail-in ballots in particular are fraudulent.

But while Trump was demanding that counting be halted in Georgia and Pennsylvania – where he is leading – his supporters and campaign insisted that it continue in Arizona and Nevada, where he is trailing.

Kicking up doubt, dragging the count

Trump has called in his lawyers to shore up his dimming re-election prospects, but legal experts said the flurry of lawsuits had little chance of changing the outcome but might cast doubt on the process.

As Trump's paths to victory narrowed, his campaign was ramping up legal challenges and said it was planning to file its latest case in Nevada.

On Wednesday, the campaign sued in Michigan, Pennsylvania and Georgia, and asked to join a pending case at the US Supreme Court.

Experts said the litigation serves to drag out the vote count and postpone major media from declaring Biden the victor, which would have dire political implications for Trump.

"The current legal maneuvering is mainly a way for the Trump campaign to try to extend the ball game in the long-shot hope that some serious anomaly will emerge," said Robert Yablon, a professor at the University of Wisconsin-Madison Law School. "As of now, we haven't seen any indication of systematic irregularities in the vote count."

Trump campaign manager Bill Stepien said in a statement on Wednesday that the lawsuits were aimed at ensuring legal votes were counted.

“The lawsuits are meritless," said Bob Bauer, who is part of Biden's legal team. "They’re intended to give the Trump campaign the opportunity to argue the vote count should stop. It is not going to stop."

Ultimately, for the lawsuits to have an impact, the race would have to hang on the outcome of one or two states separated by a few thousand votes, according to experts.

In Michigan and Pennsylvania, Trump asked courts to temporarily halt the vote counts because the campaign's observers were allegedly denied access to the counting process.

The Michigan case was dismissed on Thursday but a Pennsylvania court ordered that Trump campaign observers be granted better access to counting process in Philadelphia.

At the Supreme Court, the campaign is seeking to invalidate mail-in votes in Pennsylvania that are postmarked by Election Day but arrive by the end of Friday.

In Georgia, the Trump campaign asked a judge to require Chatham County to separate late-arriving ballots to ensure they were not counted, but the case was dismissed on Thursday.

"There is no consistent strategy there," said Jessica Levinson, a professor at Loyola Law School in Los Angeles. She said the campaign was "throwing theories at a wall to see if anything sticks for long enough to muck up the waters."