WILMINGTON, Del. — President-elect Joe Biden began seeing more support, if indirectly, from Republicans on Thursday as senior GOP lawmakers called for him to receive classified briefings even as the Trump administration continued to bar a formal transition.

Trump officials prolonged that blockade even though in private top campaign aides were candidly telling President Trump that his prospects of winning reelection were an uphill battle, according to sources close to the discussions who spoke on the condition of anonymity to reflect private conversations. His campaign, meantime, was scrambling to form a coherent legal strategy.

Late Thursday, Biden was projected as the winner in Arizona, becoming the first Democratic nominee to win the state since 1996. The Edison Research projection gives Biden 290 electoral votes to 217 for Trump. Biden’s projected win in Arizona marks the fourth state he flipped from Trump’s cache in 2016.

Taken together, those elements underscored a reality that Biden has accepted but one that Trump and key Republican officials haven’t: The current president is unlikely to overturn enough ballots in key states to undermine Biden’s presidential win.

Sen. Susan Collins (Maine), a moderate Republican who won a tough reelection bid last week, said Biden needs to be briefed on classified intelligence — calling that process the “most important part of the transition” and one that can take place even as Trump contests the results in court.

“Like any apparent winner, he should have access to office space, federal employees, materials, supplies, whatever, but the standard assistance that the apparent winner receives,” Collins told reporters on Thursday. “That doesn’t in any way preclude President Trump from pursuing his legal remedies if he believes there are irregularities, but it should not delay the transition, because we want the president-elect — assuming he prevails — to be ready on day one.”

The acknowledgments came as Biden and his team continued to map out his transition, despite the lack of official certification from the General Services Administration that would unlock the resources and access to the federal government that Biden and his team will need to fully prepare for taking office on Jan. 20.

The Post's Lisa Rein explains how the Trump administration is adding challenges to the transition process for President-elect Joe Biden. (The Washington Post)

Biden also spoke with House Speaker Nancy Pelosi (D-Calif.) and Senate Minority Leader Charles E. Schumer (D-N.Y.) in their first substantive conversation since Biden was declared president-elect, with the trio stressing the need to have a coronavirus relief package signed into law by the end of the year.

The conversation effectively inserted Biden as a central figure in the talks, while Trump continued to stay out of sight and away from governing. The three Democrats coalesced behind a unified position, in particular advocating for state and local aid — a main sticking point between Democrats and Republicans.

Biden held another notable conversation on Thursday with Pope Francis, according to the transition team. Biden, who will become only the second Catholic to assume the U.S. presidency, expressed a desire to work together on issues including poverty, climate change and immigration.

The president-elect on Thursday also traveled to Rehoboth Beach, Del., where he has a vacation home and where he is expected to stay through part of the weekend. Biden, who on Wednesday named Washington veteran Ronald A. Klain as his incoming White House chief of staff, is not expected to formally announce other administration personnel this week.

But behind-the-scenes conversations between Capitol Hill and the transition team continued to occur, and Biden’s team has also tapped a coterie of senior House and Senate Democratic officials to serve as liaisons to Hill offices until Biden officially assumes the presidency, according to congressional aides.

An informal sketch of Biden’s orbit continued to take shape, with Steve Ricchetti, who served as chief of staff for Biden during his vice presidency, expected to assume a senior adviser role and Ted Kaufman, who temporarily succeeded Biden in the Senate when he was elevated to the vice presidency, becoming the head of a kitchen cabinet of sorts on which Biden will rely, according to a person familiar with the structure. Mike Donilon, another veteran Biden hand, is also expected to be a senior adviser to the president-elect.

One intriguing name being discussed privately is former Democratic presidential nominee Hillary Clinton as the U.S. ambassador to the United Nations, according to the person familiar with the chatter who spoke on the condition of anonymity. The thinking behind the move was that it would be a way for Biden to highlight the importance of that position in his administration and that placing her there would raise the prestige of the U.N. itself at a time when global cooperation, and the U.S. role on the world stage, has ebbed.

Another name emerging as a potential Cabinet pick is Rep. Cheri Bustos (D-Ill.), the chairwoman of the House Democrats’ campaign arm who oversaw the party’s loss of House seats in the 2020 elections. She has signaled interest in leading the Agriculture Department. A spokeswoman for Bustos said, “With votes still being counted across America, Congresswoman Bustos remains focused on the task at hand and making sure front-line members in uncalled races have the support they need.”

Meanwhile, the outlook at the White House continued to remain tense.

Some aides were looking for jobs, and many were quarantining or even sickened by the fresh coronavirus outbreak within the White House. Few were continuing to fight for Trump’s reelection.

“A lot of people aren’t here,” one administration official in the West Wing said on Thursday. Trump remained sequestered Thursday, marking a week since he has spoken in public view.

At his campaign headquarters, many staffers were expected to be laid off in the coming days, two officials said, with some aides being notified on Thursday. Officials were also supposed to brief surrogates on legal strategy Thursday afternoon but postponed the call twice, a person familiar with the planning said.

Later, in a 12-minute call, campaign officials said they believed Trump could still win the race. Tim Murtaugh, the campaign spokesman, asked donors and surrogates “for patience” and said it would take some time.

“There is not going to be a silver bullet,” he said. Murtaugh spent much of his time criticizing the news media, according to an audio recording of the call.

“The campaign continues to firmly believe that this election is not over,” Murtaugh said.

Justin Clark, the deputy campaign manager overseeing the legal efforts, told listeners that “you’re going to see a lot of things happen,” without offering much in the way of specifics. Clark asked for people to send to the campaign for investigation things they see on Twitter or on other websites.

Privately, White House senior adviser Jared Kushner, the president’s son-in-law, continued to tell allies that Trump is “realistic” about his chances but wants to continue the fight, a person who has spoken to him said. Campaign manager Bill Stepien and other top campaign aides have also briefed Trump on his chances, casting them as uphill and telling Trump it is unlikely he will win.

But Trump does not want to pull out of the fight until the votes are certified in key states, which won’t be until late November or early December. His campaign filed five new lawsuits in Pennsylvania in an attempt to block 8,349 ballots in Philadelphia from being counted — complaints that centered on mail-in ballots that city officials decided to accept despite administrative errors made by voters.

Biden has been declared the winner of Pennsylvania by multiple media outlets, and he leads Trump in the state by more than 53,000 votes. Kevin Feeley, a spokesman for the Philadelphia city commissioners, said on Thursday that the disputed ballots had not yet been added to the public vote totals.

The Trump campaign ran into resistance elsewhere in the courts in Pennsylvania, as three former Republican members of Congress and several veterans of GOP administrations joined the opposition to an effort by Trump to use the federal courts to block certification of the state’s election results.

Trump alleged in a lawsuit that hundreds of thousands of votes in Democratic Philadelphia and Pittsburgh are invalid because his campaign was not able to watch them being counted, which election officials deny.

A group including former congressmen Charlie Dent and Jim Greenwood (R-Pa.) and former congresswoman Connie Morella (R-Md.), along with former New Jersey governor Christine Todd Whitman and former deputy attorney general Donald Ayer, filed a brief on Thursday asking Judge Matthew W. Brann to leave the dispute to the Pennsylvania state courts, which are considering a lawsuit from Trump on the same issue.

Another onetime Republican leader, former senator Saxby Chambliss (R-Ga.), whose state has also become a battleground over ballots that Republicans have contested, told The Washington Post in an interview that “there was no wholesale fraudulent scheme.”

Of Georgia, where Biden leads by roughly 14,000 votes and where a hand recount is underway, Chambliss, who retired at the end of 2014, said: “I am on the ground and I heard nothing about any kind of harvesting of ballots or fraudulent transactions. Sure, there are going to be isolated situations but not on a wholesale basis.”

Chambliss stopped short of saying Trump should concede or allow the transition process and security briefings for Biden to begin. He said he supported Trump’s right to pursue all legal options to contest the election. But he emphasized that the process must play out in court, and only if new evidence surfaces.

Other GOP figures went further in actively identifying Biden as the rightful winner. Republican Gov. Mike DeWine of Ohio, whose state Trump won by eight points, said on CNN on Thursday that he sees Biden as the president-elect even as Trump has “every right” to legally contest the results.

“Our courts are the best place, frankly, to adjudicate facts,” DeWine said.

But because of Trump and his team’s public defiance, many elected Republican officials have declined to even call Biden the president-elect. Even some GOP lawmakers who said Biden should be briefed were careful to distinguish between the type of intelligence Biden received as the Democratic nominee and the full-blown presidential daily briefing, which Biden would usually have access to as the president-elect.

“We should be in the same posture that we ran throughout the whole campaign, both of them receiving briefings, as they’re both trying to be able to prepare and then allow the process to be able to go through right now,” said Sen. James Lankford (R-Okla.), a member of the Intelligence Committee.

Still, the consensus among Senate Republicans on Thursday was that Biden should be privy to the nation’s classified secrets.

“I see no problem” with Biden getting briefings, said Sen. Charles E. Grassley (Iowa), the most senior Republican in the Senate.

“I think so, yes,” Sen. Lindsey O. Graham (R-S.C.), an ardent Trump ally, responded when asked whether Biden should be receiving classified briefings.

“Whether he actually gets the product itself, I think the information needs to be communicated in some way,” said Sen. John Cornyn (R-Tex.), another member of the Intelligence Committee. “If in fact he does win in the end, I think they need to be able to hit the ground running.”

Amy Gardner, John Wagner, Mike DeBonis and Felicia Sonmez contributed to this report.