Republican Sens. David Perdue and Kelly Loeffler are now attacking Georgia Secretary of State Brad Raffensperger, also a Republican, for his "mismanagement and lack of transparency" with this election and have called on him to resign.

"While blame certainly lies elsewhere as well, the buck ultimately stops with the Secretary of State. The mismanagement and lack of transparency from the Secretary of State is unacceptable," the senators said in a statement. "Honest elections are paramount to the foundation of our democracy. The Secretary of State has failed to deliver honest and transparent elections."

"He has failed the people of Georgia, and he should step down immediately," the statement continued

In response, Raffensperger said that he will not resign.

"I know emotions are running high. Politics are involved in everything right now. If I was Senator Perdue, I'd be irritated I was in a runoff. And both Senators and I are all unhappy with the potential outcome for our President," Raffensperger, the state's top elections official, said in a statement. "But I am the duly elected Secretary of State. One of my duties involves helping to run elections for all Georgia voters. I have taken that oath, and I will execute that duty and follow Georgia law."

-ABC News' Quinn Scanlan

The vice president is publicly standing by the president's side, tweeting from his personal account that he told his staff Monday: “it ain’t over til it’s over.. and this AIN’T over!”

In addition to the vice president's tweet, a senior administration official said the vice president has been very involved in the ongoing legal fight, participating in a fundraising call for the campaign's legal fund on Friday, after meeting with advisers at both the White House and campaign headquarters last week.

"The vice president has been very actively engaged with senior staff both from the campaign and the White House in discussing strategy with regard to both the recount and legal efforts," the official said.

-ABC News' Jordyn Phelps

The Trump campaign suffered another set-back in their effort to mount a legal challenge to the presidential election -- this time in Michigan.

On Friday, the campaign filed an appeal to an earlier ruling that denied their complaint regarding the access poll observers were getting to watch mail-in ballot processing. But Monday, the Michigan Court of Appeals said they still have not accepted the appeal, calling it "defective" because it lacked key documents.

John Nevin, the communications director for the Michigan Supreme Court, told ABC News that the appeal will not be considered by the court until the missing documents, which include a copy of the judgement order, a copy of the registrar of actions, a copy of the transcript and -- most importantly -- a copy of the brief, have been filed.

"It's missing the most important part," Nevin said.

Mark F. Hearne II, the lawyer on the case, did not immediately respond to ABC News' request for comment.

In this suit, the campaign was seeking to have Michigan Secretary of State Jocelyn Benson direct local clerks to allow election challengers to observe the vote processing and counting process and to view the video records of ballot drop boxes.

The task of opening mail-in ballots is largely completed, the court had noted in its ruling, but the Trump campaign argued in the appeal that their effort is not pointless "because review and certification of election results continues… (and) review of absent uniformed services voter or overseas voter ballots is ongoing. Review of these ballots must be performed by bipartisan teams of election inspectors."

The court had also ruled that, even if relief was warranted, the campaign sued the wrong person -- Secretary Benson does not have the authority to tell local polling officials what to do and the campaign would instead have to go directly to each jurisdiction.

In their reply, which has not yet been accepted by the court, the Trump campaign attorneys argued that it would be unreasonable to expect them to file individual lawsuits in dozens of Circuit Courts against each of the 1,603 county and local election officials in Michigan, the appeal states.

Contrary to the Court of Claims order, Michigan law provides that the Secretary of State is the "chief elections officer" responsible for overseeing the conduct of Michigan elections, the appeal said.

Notably, the appeal did not address the court's issue with the evidence presented in the case, which the judge had called hearsay "at best."

-ABC News' Olivia Rubin

Biden warns of 'dark winter' ahead as he lays out COVID-19 plan, calls for unity on masks

President-elect Joe Biden in his first solo remarks to Americans since his victory speech over the weekend reminded Americans of the ongoing coronavirus pandemic as cases and hospitalizations rise across the country, and said the country is “still facing a very dark winter” before offering his plan to combat it.

"We are ready to get to work addressing the needs of the American people. Today, that work begins," Biden said from The Queen Theater in Wilmington Delaware, following a briefing with his newly-announced COVID-19 advisory board. "It starts with doing everything possible to get the COVID-19 under control, so that we can reopen our businesses safely and sustainably, resume our lives, put this pandemic behind us."

While he praised the announcement from Pfizer Monday morning that the company has a vaccine in trial that looks "90% effective in preventing COVID-19," Biden reminded that even if the vaccine is approved, it will not be widely available for months. He went on to urge all Americans, regardless of whether they voted for him, to "end the politicization of basic responsible public health steps."

"This election is over. It’s time to put aside the partisanship and the rhetoric that’s designed to demonize one another," Biden said, reminding Americans to keep social distancing and wearing a mask.

"Doesn't matter who you voted for, whether you stood, where you stood before election day, doesn't matter your party, your point of view. We can save tens of thousands of lives if everyone would just wear a mask for the next few months. Not Democrat or Republican lives, American lives," he added. "A mask is not a political statement but it is a good way to start pulling the country together."

After pledging to rejoin the World Health Organization on "Day One," Biden also said his advisory board will include experts on global health security, "so that we can restore U.S. global leadership to fight this pandemic" -- in sharp contrast to Trump's isolationist approach to the virus and general policy.