Before introducing his Justice Department picks from Wilmington, Delaware, on Thursday, Biden offered comments on Wednesday's chaos at the Capitol which he deemed "one of the darkest days in the history of our nation" and "an unprecedented assault on our democracy."

"All of us here grieve the loss of life, grieve the desecration of the people's house. But what we witnessed yesterday was not dissent. It was not disorder. It was not protests. It was chaos," Biden said. "They weren't protesters. Don't dare call them protesters. They were a riotous mob, insurrectionists, domestic terrorists."

Biden placed blame on Trump who, he said, for the past four years has "made his contempt for our democracy, our Constitution, the rule of law clear in everything he has done."

"He unleashed an all-out assault on our institutions of our democracy from the outset. And yesterday was but the culmination of that unrelenting attack," Biden said.

Biden also predicted the response would have been very different had the majority of rioters been Black.

"No one can tell me that if it had been a group of Black Lives Matter protesting yesterday, there wouldn't have been -- they would have been treated very, very differently than the mob of thugs that stormed the Capitol. We all know that's true, and it is unacceptable, totally unacceptable," he said.

House Speaker Nancy Pelosi has called on Vice President Mike Pence to invoke the 25th Amendment to remove Trump from office for his "seditious acts" following Wednesday's rioting at the Capitol, she said at a press conference Thursday.

The California Democrat is threatening impeachment proceedings if Pence does not.

-ABC News' Mariam Khan

Senate Majority Leader Mitch McConnell put out a statement Thursday, saying the riots within the Capitol Building Wednesday represent "a massive failure" of "institutions, protocols, and planning that are supposed to protect the first branch of our federal government."

"A painstaking investigation and thorough review must now take place and significant changes must follow," McConnell added. "Initial bipartisan discussions have already begun among committees of oversight and Congressional Leadership."

-ABC News' Allison Pecorin

Transportation Secretary Elaine Chao is resigning from her position in the wake of rioting at the U.S. Capitol.

She cites the storming of the Capitol by "supporters of the President" as an "entirely avoidable event" in a letter she is sending out to her colleagues announcing her resignation.

"Yesterday, our country experienced a traumatic and entirely avoidable event as supporters of the President stormed the Capitol building following a rally he addressed. As I'm sure is the case with many of you, it has deeply troubled me in a way that I simply cannot set aside," Chao said.

Chao is married to Senate Majority Leader Mitch McConnell.

Rep. Liz Cheney, R-Wyo., a member of House GOP leadership and one of the first prominent Republicans to acknowledge Biden's victory, sent a 21-page memo to her conference making the case against a challenge to the Electoral College certification process on Wednesday, arguing that it would improperly overrule states' authority over elections, and set a "dangerous precedent" down the line for future elections and sessions of Congress.

"By objecting to electoral slates, members are unavoidably asserting that Congress has the authority to overturn elections and overrule state and federal courts. Such objections set an exceptionally dangerous precedent, threatening to steal states’ explicit constitutional responsibility for choosing the President and bestowing it instead on Congress," Cheney wrote.

"This is directly at odds with the Constitution’s clear text and our core beliefs as Republicans. Democrats have long attempted, unconstitutionally, to federalize every element of our nation—including elections. Republicans should not embrace Democrats’ unconstitutional position on these issues," she added.

Cheney raises questions about the proposal from some Republicans to set up a commission to investigate concerns about the election, calling it a "problematic" set up that would take much longer than ten days to wrap up, and potentially delay the inauguration. The memo also exhaustively summarizes the court rulings against the president's legal efforts in the six states Republicans plan to target on Wednesday: Arizona, Nevada, Wisconsin, Michigan, Georgia and Pennsylvania.

-ABC News' Benjamin Siegel