A growing list of Republicans on Capitol Hill are putting pressure on Trump to allow the transition process to begin for Biden, giving him access to intelligence briefings and pandemic planning despite the president clinging to power.

Sen. Mitt Romney, a frequent Trump critic and the only Republican to vote to remove Trump from office in his impeachment trial, issued a strong rebuke  late Thursday of the president’s move to invite Michigan lawmakers to the White House, saying, “It is difficult to imagine a worse, more undemocratic action by a sitting American President.”

Sen. Ben Sasse of Nebraska, another Republican who has publicly feuded with Trump, urged Americans to look at what the president’s legal team is saying in court, not during press conferences, “because there are legal consequences for lying to judges” preventing them from making unfounded claims of widespread fraud.

"No, obviously, Rudy and his buddies should not pressure electors to ignore their certification obligations under the statute," Sasse said in a statement late Thursday. "We are a nation of laws, not tweets."

In an interview with Fox News Radio Thursday, Joni Ernst, an Iowa Republican and ally of Trump's, also called the barrage of accusations from Trump’s lawyers “offensive” and “absolutely outrageous.”

And while retiring Republican Sen. Lamar Alexander is still unwilling to outright claim Biden won the election, he said in a statement Friday, "it looks like he has a very good chance” and that Biden should start receiving transition materials, which he said is particularly necessary in the coming months for vaccine distribution. On Thursday, he also told Know News, a Tennessee news outlet, he hasn't seen any evidence of widespread voter fraud.

Democrats have also ramped up their rhetoric with House Majority Leader Steny Hoyer telling Capitol Hill reporters he believes the president’s actions “border on treason” and that he is “undermining the very essence of democracy.”

-ABC News' Allison Pecorin and Mariam Khan

During her press conference on Capitol Hill Friday morning, House Speaker Nancy Pelosi was asked if the House of Representatives will have an "expanded" role if Trump continues to derail the Biden transition and refuses to concede.

"Yes," Pelosi said. "I'm not one to show my hand, but nonetheless, we're ready. We're ready."

She did not elaborate any further on the potential involvement.

Pelosi also told reporters that she and Senate Minority Leader Chuck Schumer plan to discuss the lame duck session and urgency of COVID-19 relief with Biden and Vice President-elect Kamala Harris later this afternoon in Wilmington, Delaware.

-ABC News' Mariam Khan

In a post-election briefing Friday morning, Bob Bauer, a senior adviser to the Biden team, tore into Trump’s strategy of trying to influence Michigan lawmakers to subvert the will of its voters but maintained that "there's no way whatsoever" Trump will be successful in overturning the election.

“It's an abuse of office, it's an open attempt to intimidate election officials. It's absolutely appalling -- actually in the context of all these losses and the record of failure that I just described -- it's also pathetic. But, having said all of that, it will be unsuccessful,” Bauer said.

Bauer, former White House counsel in the Obama administration, said no state legislature in history has attempted to subvert the will of its voters and appoint their own slate of electors to send to Washington when the Electoral College meets in December.

“Now, the reason it's never happened before, is that it cannot be done. The Constitution does not permit a state legislature to do what Donald Trump wants the Michigan State Legislature to do,” Bauer said. “Not possible, not legal, not constitutional, cannot happen.”

He warned that Trump's ongoing lawsuits aren’t enough to change results but will harm election credibility. He took aim at the press conference held by Trump’s attorneys at the Republican National Committee Thursday, calling it an “embarrassment.”

“The political claims they’re making are bordering on the ludicrous and the absolutely comic. Anybody who wanted to treat themselves to the theater of the absurd tuned in,” he said. "While the president and his allies are ripping at the fabric of democracy any way they can, the fabric is not tearing. It is holding firm."

Bauer also said the “targeting of the African American community" by the Trump campaign "is not subtle,” referring to lawsuits and recounts in predominantly Black counties which overwhelmingly went for Biden.

"It's quite remarkable how brazen it is," Bauer said. "This is straight out discriminatory behavior."

-ABC News' John Verhovek, Molly Nagle and Beatrice Peterson

Despite the Trump adminstration blocking his ascertainment as president-elect, Biden is forging ahead with his transition to the White House, announcing four new members of his incoming senior staff Friday morning.

Carlos Elizondo will serve as White House social secretary, the first Latino American appointed to the position. He served worked as a special assistant to the president and social secretary to the vice president for all eight years of the Obama-Biden administration.

Cathy Russell, who sits on the advisory board of the Biden-Harris transition team and worked on the campaign, is joining as director of the White House Office of Presidential Personnel. Russell served at the White House and Department of State throughout the Obama-Biden administration.

Louisa Terrell will serve as director of the White House Office of Legislative Affairs. She served as a special assistant to the president for Legislative Affairs in the Obama-Biden administration and worked for several years on Capitol Hill.

The Biden campaign also announced Jill Biden’s policy director, Mala Adiga, who served as a senior adviser to Jill Biden and a senior policy adviser on the Biden-Harris campaign.

As speculation soars surrounding Biden's cabinet, he revealed on Thursday that he and his team have made a decision on who will serve as the Treasury Secretary and said it would be announced just before or just after Thanksgiving, adding that it will be someone who will be accepted across the Democratic Party.

-ABC News' Molly Nagle

When ABC News Chief Anchor George Stephanopoulos asked former New Jersey Governor and ABC News Contributor Chris Christie if it was time for Trump's challenges to the election results to end, he agreed.

"Yes. And here's the reason why the president has had an opportunity to access the courts," Christie said on ABC's "This Week" Sunday. "And I said to you -- you know, George, starting at 2:30 a.m. on Wednesday morning, if you've got the evidence of fraud, present it."

"What's happened here is quite frankly -- the conduct of the president's legal team has been a national embarrassment," he added.