Donald Trump has made a series of unsubstantiated allegations claiming he is being cheated out of re-election and calling for the outcome to be decided by the Supreme Court.

The Republican alleged he was the victim of interference from “phony polls” along with “big media, big money and big tech” after his campaign launched a series of legal challenges in key states.

In a news conference late on Thursday, he said: “If you count the legal votes I easily won. If you count the illegal votes, they can try to steal the election from us.”

Live updates as election still too close to call

He later tweeted: “I easily WIN the Presidency of the United States with LEGAL VOTES CAST. The OBSERVERS were not allowed, in any way, shape, or form, to do their job and therefore, votes accepted during this period must be determined to be ILLEGAL VOTES. US Supreme Court should decide!”

The presidential election remains too close to call after polls closed on Tuesday, but Joe Biden remains the favourite after clinching three key battleground states.

Pennsylvania was expected to announce its result later on Friday. If it goes to Mr Biden, he wins the race to the White House.

Here, Sky News looks at the Trump campaign’s legal challenges and asks experts if they are likely to succeed.

Which states has Donald Trump launched legal action in?

Georgia

The Trump campaign filed a lawsuit to require Chatham County, which includes the city of Savannah, to separate and secure late-arriving ballots to ensure they are not counted.

They are challenging 57 absentee ballots.

Nevada

The Trump campaign asked for emergency relief to stop the counting of “improper votes” in Democrat-leaning Clark County, home to Las Vegas, and said it was filing a federal lawsuit.

It said it had evidence that “thousands of people” cast ballots who no longer live in the state or are dead.

The Trump campaign also said people have taken other voters’ mail-in ballot papers and voted falsely under their names, with others sending “up to 18 ballots”.

Pennsylvania

Mr Trump’s campaign has asked the US Supreme Court to allow it to join a pending lawsuit filed by Pennsylvania Republicans over whether the battleground state should be permitted to accept ballots that were mailed by election day, but arrived late.

They also wanted more access for Republican observers.

Mr Trump’s campaign manager from 2016, Cory Lewandowski, arrived at the Pennsylvania Convention centre with a court order which he said gave him permission to enter the Philadelphia count.

He told Sky News’ Mark Stone: “We’ll see if fraud is taking place.”

Wisconsin

Trump campaign manager Bill Stepien said the campaign would request an immediate recount of the vote in Wisconsin.

He cited “reports of irregularities in several Wisconsin counties which raise serious doubts about the validity of the results”.

Michigan

The Trump campaign has lost a lawsuit to halt vote-counting in Michigan.

Michigan Court of Claims Judge Cynthia Stephens made the ruling during a hearing, saying she plans to issue a written ruling tomorrow.

Joe Biden is projected to win the state with 99% of votes counted.

What have the experts said?

Lawrence Douglas, law professor and author of Will He Go? Trump And The Looming Election Meltdown In 2020

Professor Douglas told Sky News: “The lawsuits seem frivolous without any real chance of materially affecting the outcome of the election.

“The only thing they can do is delay matters and further muddy the waters – which might be Trump’s aim in the first place.”

Professor Robert Tsai, law professor at the American University Washington College of Law

He said: “From my examination of the lawsuits so far, they look like a bit of a desperation ploy.

“The margins are not particularly close anywhere except Nevada and as those counts are still trickling in, it looks like they’re going Biden’s way.

“If you look at the substance of the lawsuits that have been filed, they are mostly alleging under state laws that there has perhaps been inappropriate or insufficient access to polling stations – but these have been thrown out pretty consistently so far.

“I don’t see thousands of votes changing or being thrown out from what I’ve seen.”

Jessica Levinson, professor at Loyola Law School in Los Angeles

Professor Levinson said the Trump campaign was “throwing theories at a wall to see if anything sticks for long enough to muck up the waters”.

She added: “There is no consistent strategy there.”

Edward Foley, specialist in election law at the Moritz College of Law

Mr Foley said the cases might have merit but only affected a small number of ballots and procedural issues.

He added: “But merit in that sense is very different from having the kind of consequence that Bush v.Gore did in 2000.”

Carol Laham, partner in Wiley Rein LLP’s nationally-recognized Election Law & Government Ethics Practice

Ms Laham told Sky News: “Every state has its own requirements for the conduct of the election in that state, and the Trump campaign must prove that the election is not being conducted in accordance with the state requirements.

“If the campaign has sufficient evidence to prove the violation alleged then it has a chance of being successful on the merits.”

David Weinstein, former assistant US attorney for the southern district of Florida

Mr Weinstein told Sky News: “They all have a long shot to get anywhere here.”

He added: “As far as recounts go, it’s not even close in any of these states.”