Biden will nominate Rep. Marcia Fudge, D-Ohio, to lead the Department of Housing and Urban Development, sources familiar with the president-elect's decision told ABC News.

Fudge, who had campaigned openly to become the first Black secretary of agriculture, would be the second member of the Congressional Black Caucus to join the Biden administration, following Rep. Cedric Richmond, D-La., a key Biden surrogate who will serve as a senior White House official.

She would be Biden's third African-American cabinet nominee, after Linda Thomas-Greenfield, his pick to serve as U.S. ambassador to the United Nations, and retired Army Gen. Lloyd Austin, who he said Tuesday would be his nominee to lead the Pentagon.

The move would put Fudge at the helm of the $50 billion department as the country faces a potential housing crisis in the new year -- with many Americans struggling to pay rent, and others worried they will not be able to do so in the next few months as the economy continues to languish due to the coronavirus pandemic.

Approached by reporters on Capitol Hill Tuesday, Fudge said she hadn't been formally offered the job by Biden, but said the two had spoken previously.

"If I were to be named, certainly it's an honor and a privilege to be asked to be in a president's Cabinet," she said. "If I can help this president in any way possible, I am more than happy to do it."

Fudge, a member of the House Agriculture Committee and Committee on Education and Labor, represents the Cleveland area, as well as Akron, Ohio.

When she was openly campaigning for the nomination to lead the department of agriculture, she lamented the possibility of leading HUD.

"As this country becomes more and more diverse, we're going to have to stop looking at only certain agencies as those that people like me fit in. You know, it's always 'we want to put the Black person in labor or HUD,'" she told Politico last month.

Fudge's move to the Biden administration would further tighten House Speaker Nancy Pelosi's fragile majority, making it even harder for Democrats to pass any legislation until Fudge's replacement is seated later next year.

"I'm in a safe district," Fudge told reporters. "We're just hopeful that if this works out the way we'd like it to, that it will be OK."

-ABC News' Benjamin Siegel, Katherine Faulders, Beatrice Peterson and John Verhovek

In a single, succinct order, the U.S. Supreme Court has shut down an 11th-hour attempt by allies of Trump in Pennsylvania to block its slate of certified electors and toss out 2.5 million mail-in ballots.

"The application for injunctive relief presented to Justice Alito and by him referred to the Court is denied," the court said.

The appeal -- brought by U.S. Rep. Mike Kelly, a Pennsylvania Republican, along with another GOP candidate for Congress -- alleged that the state legislature did not legally pass the law allowing for expanded mail-in voting during the pandemic. They sought the justices to order all mail-in ballots thrown out along with the state's official certification of election results, which was signed by Gov. Tom Wolf last week.

The Supreme Court's denial comes on the same day the state of Texas filed suit against four battleground states alleging that they "exploited the COVID-19 pandemic" to improperly loosen election rules and skew the contest's outcome. Justices have not yet said whether they will hear the case.

The actions come on the Dec. 8 "safe harbor" deadline by which states must lock in the slate of electors they intend to send to Congress to affirm the election results -- selections that are intended to match the will of the voters.

-ABC News' Devin Dwyer, Alex Hosenball, Olivia Rubin and Matthew Mosk

Shortly before releasing his press release confirming retired four-star Gen. Lloyd Austin as his pick to lead the Pentagon, The Atlantic magazine published an op-ed penned by Biden op-ed, laying out the reasons behind his choice and noting their history together in the Obama administration.

“Today, I ask Lloyd Austin to once more take on a mission for the United States of America—this time as the secretary-designate of the Department of Defense. I know he will do an outstanding job,” Biden wrote.

Austin, the former commander of U.S. Central Command -- with jurisdiction over military activities in the Middle East -- retired in 2016 after more than 40 years of military service. If confirmed, he would be the first African American to lead the Pentagon.

Biden pointed to Austin’s ”many strengths and his intimate knowledge of the Department of Defense and our government” as factors that made him “the person we need in this moment," saying his experience leading the Iraq drawdown prepares him for coordinating vaccine distribution and connecting with American families.

“And the next secretary of defense will have to make sure that our armed forces reflect and promote the full diversity of our nation. Austin will bring to the job not only his personal experience, but the stories of the countless young people he has mentored. If confirmed, he will ensure that every member of the armed forces is treated with dignity and respect, including Black, Latino, Asian American, Native American, women, and LGBTQ service members," Biden wrote.

Biden also seemed to address the fact that Lloyd’s nomination would require a waiver given his recent military service -- something that some Democrats have already expressed opposition to.

“I respect and believe in the importance of civilian control of our military and in the importance of a strong civil-military working relationship at DoD—as does Austin," he wrote.

"Austin also knows that the secretary of defense has a different set of responsibilities than a general officer and that the civil-military dynamic has been under great stress these past four years," Biden added.

The announcement comes as Biden and Vice President-elect Kamala Harris meet with civil rights leaders who have pushed Biden to name more people of color to senior-level Cabinet positions.

-ABC News' Molly Nagle

Trump this afternoon kicked off a self-congratulatory vaccine "summit" to tout the speed at which COVID-19 vaccines were produced -- speaking at the same time Biden was introducing his key health appointments and nominees.

The room in the Eisenhower Executive Office Building on the White House complex was packed for the three-hour event, and it appeared almost everyone was wearing a mask, save for Trump.

Asked why no members of the Biden transition were invited to participate, the president falsely claimed he won the election and that he won key swing states where Biden actually was victorious.

“We’re gonna have to see who the next administration is because we won in those swing states -- and there was terrible things that went on. So we’re gonna have to see who the next administration is,” Trump said. “But whichever the next administration is will really benefit by what we’ve been able to do with this incredible science.”

“We were rewarded with a victory,” Trump continued. “Let's see whether or not somebody has the courage -- whether it's legislatures or a justice of the Supreme Court or a number of justice of the Supreme Court. Let's see if they have the courage to do what everybody in this country knows is right.”

To date, Trump, his campaign and its allies have seen at least 38 defeats in court.

-ABC News' Ben Gittleson and Jordyn Phelps

Trump and Biden hold dueling events on the pandemic response Tuesday with the president hosting a "vaccine summit" at the White House, just days before a Food and Drug Administration advisory committee holds a hearing on whether to authorize emergency use of a COVID-19 vaccine, while the president-elect is slated to formally roll out his health care picks who will take over handling the COVID-19 pandemic in 43 days.

At his event, Trump is slated to sign an executive order touting his mantra of "America First" that would prioritize Americans’ access to COVID-19 vaccines before the United States helps other countries. But the chief science adviser to "Operation Warp Speed," the U.S. government's initiative to expedite vaccine development which Trump is also expected to tout, said Tuesday morning he doesn't know about the vaccine-related executive order Trump is expected to sign.

"Frankly, I don't know and, frankly, I'm staying out of this. I can't comment," Dr. Moncef Slaoui told ABC News Chief Anchor George Stephanopoulos in an interview Tuesday on "Good Morning America,” when asked to explain the executive order.

The event comes as a senior administration official familiar with the matter confirmed reporting to ABC News that the Trump Administration passed when Pfizer offered in later summer to sell the U.S. more COVID-19 vaccine doses -- an approach which the White House has denied and Slaoui defended Tuesday. Representatives of Pfizer and Moderna -- the two drug companies seeking emergency-use authorization -- are not expected to attend the White House summit, nor is anyone from the Biden transition team.

Biden, meanwhile, is slated to introduce the health care team he will entrust with handling the pandemic California Attorney General Xavier Becerra as Health and Human Services secretary, the first Latino to hold the post if confirmed. Director of the National Institute of Allergy and Infectious Diseases Dr. Anthony Fauci, who is taking on the elevated role of chief medical adviser to Biden in the incoming administration, is expected to dial into Biden’s meeting, though not the one at the White House.

Biden and Vice President-elect Kamala Harris are also meeting Tuesday with several civil rights leaders including NAACP representatives to discuss policy issues around racial equity as well as diversity and representation on the incoming Cabinet. It comes after news leaked that Biden is expected to name retired four-star Army Gen. Lloyd Austin as his defense secretary, who would be the first African American in the post if confirmed, this week.

Tuesday is also the congressionally mandated "safe harbor" deadline -- the date, under federal law, by which the "final determination of any controversy or contest concerning the appointment" of electors "shall be conclusive” -- making it extremely difficult to dispute election results in the courts, where pro-Trump efforts have seen at least 39 defeats to date.