Attorney Sidney Powell was back at the White House Sunday to push President Donald Trump and his administration to issue an executive order to seize voting machines for examination, two sources with direct knowledge tell ABC News.

It is unclear if Powell met face-to-face with the president Sunday.

She met with Trump in the Oval Office Friday night and was joined by Trump's former national security adviser, retired Lt. Gen. Michael Flynn.

Sources, who were against the move Friday evening, were stunned to hear Powell was back in the building Sunday.

Critics expressed alarm at Friday's meeting, which was first reported by The New York Times. Noah Bookbinder, who heads the watchdog group Citizens for Responsibility and Ethics in Washington, told ABC News that the ideas raised in the Oval Office would represent an "abuse of power" and were "wrong and must be condemned."

- ABC News' John Santucci, Katherine Faulders

Speaking Sunday on "This Week with George Stephanopoulos," former Michigan Gov. Jennifer Granholm, who was just announced as nominee for Energy Secretary in President-elect Biden's administration, said Biden had "robust"plans for addressing climate change and responding to the massive SolarWinds hack.

"The civil servants, the investigators, the scientists who are doing the investigation, they've got to be able to come up with very specific answers so we know what the response will be. But Joe Biden I know will have a robust response once we find out the perpetrator and extent of it," Granholm said about the cyberattack.

On Biden's plans to address climate change, Granholm said, "The Green New Deal was an important framework for what Joe Biden has put on tap, but I mean really, this is the most robust climate change plan ever."

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-Molly Nagle (edited)

Sen. Mark Warner, the top Democrat on the Senate Intelligence Committee, joined with Secretary of State Mike Pompeo and his Republican Intelligence Committee counterpart, Sen. Marco Rubio, on "This Week" Sunday in placing the blame for the government cyberattack on Russia, despite President Trump's downplaying of the country's involvement Saturday.

"I would echo what Secretary Pompeo has said and Marco Rubio has said. All indications point to Russia," Warner said. "This is extraordinarily serious, and when the president of the United States tries to deflect or is not willing to call out the adversary as we make that attribution, he is not making our country safer," he further said.

The senator also told George that the intrusion "may be ongoing" and that, despite current indications that only "non-classified networks" were breached, the attackers nevertheless got away with a "big, big haul" and that it could be some time before the government is able to fix the underlying vulnerabilities.

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- Adam Kelsey

Wrapping up Saturday's event announcing members of the incoming administration's climate and energy team, Vice President-elect Kamala Harris emphasized how forceful Biden's plan is in fighting climate change.

"Part of the reason I was so proud to join Joe Biden as his running mate was because he was proposing one of the most ambitious climate plans in history, a plan to secure carbon pollution-free electricity by 2035, a plan to achieve net-zero emissions no later than 2050, a plan to invest in a clean energy future and create millions of good-paying union jobs along the way," she said.

"And the team that President-elect Biden and I are announcing today will help make that plan a reality," Harris added.

The vice president-elect said the appointees and nominees announced Saturday represented some of the country's "most seasoned public servants and climate experts" and reflected the "very best of America."

"They are compassionate leaders who understand that, ultimately, addressing climate change is about building safer communities and healthier communities and thriving communities for all Americans," Harris said.

Starting at 10 a.m. ET and rolling through the day, electors cast their votes on Monday for president and vice president in state capitols across the country -- another step towards enshrining Biden's victory and a step that will happen irrespective of Trump's last-ditch effort to overturn the result.

Biden is slated to deliver remarks on the Electoral College vote certification and "the strength and resilience of our democracy" from Wilmington, Delaware, around 8 p.m. Trump has an executive order signing on his schedule and has continued to air his grievances with the election on Twitter.

Monday's casting of electoral votes is traditionally little more than a formality with federal law requiring electors to meet the "Monday after the second Wednesday in December of presidential election years" -- but as Trump resists his defeat at every turn and wages long-shot legal battles with baseless claims of fraud, the meeting comes at a tense and fragile moment for the country's democratic institutions. Biden’s margin of victory in the Electoral College is expected to be 306 votes to Trump's 232, if there are no surprises.

Electors gather in each of their respective states and the nation's capital to cast separate paper ballots for president and vice president at places determined by the state legislature. Most of the meetings will be on cam via livestream and in the middle of a pandemic, but in Michigan, another threat interrupted the plan.

Officials announced late Sunday that the state legislature's office buildings will be closed due to "credible threats of violence" after Michigan’s 16 electors meeting were scheduled to cast their ballots at the state Capitol in Lansing. In Arizona, electors were given an undisclosed location to meet and cast their ballots in an effort to avoid any confrontation with protesters.

It's unclear how Trump's allies and supporters, particularly those in Congress who have fallen in line with his refusal to accept the loss -- despite Friday's final rejection at the Supreme Court -- will respond to Biden's victory once the Electoral College voting is complete.

-ABC News' Kendall Karson