There is no evidence of compromised ballots or corrupt voting systems in the US election, officials said Thursday, as a top Democrat accused Republicans who refuse to accept President-elect Joe Biden's win of "poisoning" democracy.

Their messages came hours after President Donald Trump once again cried foul, retweeting a baseless claim that an election equipment maker "deleted" 2.7 million votes for him nationwide.

With most Republican lawmakers having yet to acknowledge Biden's win, Senate Minority Leader Chuck Schumer, the chamber's top Democrat, accused them Thursday of "denying reality" and "auditioning for profiles in cowardice."

"Instead of working to pull the country back together so that we can fight our common enemy Covid-19, Republicans in Congress are spreading conspiracy theories, denying reality and poisoning the well of our democracy," he said.

Senior US federal and state election officials meanwhile in a statement rejected Trump's claims of fraud, saying that "the November 3rd election was the most secure in American history."

The statement was issued by the Election Infrastructure Government Coordinating Council, a public-private umbrella group under the primary federal election security body, the Cybersecurity and Infrastructure Security Agency (CISA).

"There is no evidence that any voting system deleted or lost votes, changed votes, or was in any way compromised," they said.

"While we know there are many unfounded claims and opportunities for misinformation about the process of our elections, we can assure you we have the utmost confidence in the security and integrity of our elections, and you should too," the statement said.

It was signed by the heads of the National Association of State Election Directors and the National Association of Secretaries of State -- the officials who manage elections at the state level -- and by the chairman of the US Election Assistance Commission.

- 'Absurd circus' -

The statement came just hours after Trump's retweet, which in addition to claiming 2.7 million "deleted" votes also said hundreds of thousand had been switched from him to Biden in Pennsylvania and other states.

It was the latest in a series of bogus assertions Trump and Republicans have put forth in order to reject Biden's victory.

Republican lawmakers such as Senate Majority Leader Mitch McConnell have stood firm with Trump by supporting his refusal to concede and backing his legal challenges.

Democratic House Speaker Nancy Pelosi weighed in Thursday to demand Republicans stop what she called an "absurd circus" and turn to combatting the pandemic.

"Now that the people have expressed their views, Joe Biden has won (and) Kamala Harris will be the first woman vice president of the United States," Pelosi said. 

Political experts believe Republicans may be invoking such a strategy as a way to rile up Trump's base before two US Senate runoff elections in Georgia that will determine which party controls the chamber.

A total of 161 former national security officials, including some who worked with Trump, additionally warned the current administration's continued delay in recognizing Biden's victory is posing "a serious risk to national security."

In a letter, the group including ex-Pentagon chief Chuck Hagel and Trump's former National Security Council senior counterterrorism director Javed Ali urged General Services Administration chief Emily Murphy to recognize Biden as the apparent president-elect.

Without a GSA signoff, transition funds and other resources including access to intelligence briefings cannot flow to Biden and his team, but Murphy has refused to budge.

Trump election lawyers on trial in court of public opinion

Written in giant capital letters, it's nearly impossible to miss the message emblazoned along a San Francisco street: "Jones Day: Hands off our ballots." 

The Jones Day law firm on the receiving end of the painted directive is working on US President Donald Trump's legal crusade against the outcome of last week's presidential election. 

The outgoing president and most Republican allies have so far refused to recognize the win of Democratic President-elect Joe Biden, decrying massive "fraud" and launching a dozen complaints in several key states. 

But the judicial fight is lacking one important element: any evidence pointing to such fraud.

That fact has put the lawyers of Jones Day and other firms involved in a bind, with political activists and legal colleagues alike accusing them of undermining democracy. 

The anti-Trump Republican group The Lincoln Project denounced Jones Day and Porter Wright -- another law firm assisting Trump's effort -- on Twitter. 

"Employees of @JonesDay & @PorterWright, do you believe your law firms should be attempting to overturn the will of the American people?"

And even other attorneys have challenged their peers' involvement.

"The deeper they venture down the Trump conspiracy rabbit hole, armed with nothing more than futile lawsuits premised on flimsy evidentiary or legal bases, the more their professional reputations and law licenses are at risk," lawyers Bradley Moss and Joanne Molinaro warned in an opinion piece in The Atlantic.

- 'Frivolous' -

The American Bar Association's code of ethics prohibits lawyers from bringing "frivolous" assertions -- claims without legal merit or evidence -- before a court, according to Joshua Davis at the Center for Law and Ethics at the University of San Francisco. 

"A lot of these (Trump election) cases... seem to come very close to the line and maybe cross the line into being frivolous," according to Davis.

It is rare, however, for judges or bars to impose sanctions for violating this standard, and Davis told AFP it is unlikely they would want to insert themselves into "that sort of a political mess" now. 

Fordham University law professor Bruce Green has a different dispute with the cases.

"I think the real criticism is not so much that they're frivolous," he said, "but that they're not going to prevail." 

"And even if they prevail, they wouldn't change the election result," Green said, noting that the lawyers were likely motivated by their allegiance to the Republicans, with their work boosting the party's fundraising efforts amid the polarizing legal battle.

That doesn't mean those motives can't be questioned, Green said.

"Why are they using their professional talent on these cases, rather than something more worthy of their time and abilities?" he asked. 

"But that's not a legal question."

- 'Ideological sympathies' -

The two firms have defended their positions. 

"Porter Wright has a long history of election law work during which we have represented Democratic, Republican and independent campaigns and issues," it told AFP in an email. 

In a statement, Jones Day explained the firm is not involved "in any litigation alleging voter fraud," but simply representing the Pennsylvania Republican Party in "an important and recurring rule-of-law question under the US Constitution" relating to mail-in ballots. 

Pennsylvania is a linchpin in Trump's efforts to cast doubt on the electoral process -- and where courts are reviewing many Democratic voters' choice to mail in their ballots due to the coronavirus pandemic. 

Several Jones Day lawyers have served in the Trump administration, including former White House legal advisor Don McGahn. 

And the firm has donated more than $4 million to the Republican Party this year, according to the Federal Election Commission. 

"I don't think it's money," Stephen Gillers, a legal ethics professor at New York University, speculated. "(Jones Day) does not need this business."

"I think some of what it does may be driven, in part, by ideological sympathies on the part of the lawyers," he said, given some partners' relationship to the Republican Party. 

Their work on the case is "perfectly legal and ethical," he said. 

"The problem that Jones Day faces is that it can hurt its reputation," Gillers said, noting that clients or potential hires may be turned off after this episode.

Trump's legal battles on this front are unusual -- and for some, alarming -- in a country accustomed to mostly smooth transfers of power, even between political rivals. 

But, "there are 1.3 million lawyers in the United States," Gillers said. "If Jones Day turned down the work, another firm would accept it."