Biden’s transition team has officially revealed the president-elect's choices for his incoming Cabinet. The selections announced Monday include:

"Their accomplishments in diplomacy are unmatched, but they also reflect the idea that we cannot meet the profound challenges of this new moment with old thinking and unchanged habits -- or without diversity of background and perspective," Biden said in a statement.

The team also said Biden and Vice President-elect Kamala Harris will introduce the nominees at an event that will be live-streamed Tuesday at 1 p.m. ET.

Sen. Rob Portman of Ohio, an institutionalist Republican and avid Trump supporter, wrote in an op-ed for The Cincinnati Enquirer Monday that it's time to "move forward" with Biden's transition.

"Based on all the information currently available, neither the final lawful vote counts nor the recounts have led to a different outcome in any state. In other words, the initial determination showing Joe Biden with enough electoral votes to win has not changed," Portman wrote.

Though he did not refer to Biden as “president-elect,” Portman went on to say it's "time to expeditiously resolve any outstanding questions and move forward."

"My hope is that all of us, as Americans, regardless of who we supported in the campaign, will be willing to accept the result because a thorough process was followed and the final vote count was clear," he added.

Portman is the latest Senate Republican to join a small but growing list calling for a full and formal transition process to begin. Trump's barrage of lawsuits has not swayed the court, resulting in just one win and at least 30 losses by an ABC News count.

-ABC News' Trish Turner

Biden’s White House senior staff is expanding ahead of his Cabinet announcement Tuesday. His transition announced two deputy directors of the White House Office of Legislative Affairs: Reema Dodin and Shuwanza Goff.

Dodin served as deputy chief of staff and floor director to the Senate Democratic Whip, Sen. Dick Durbin.

Goff served as floor director for the House of Representatives under House Majority Leader Steny Hoyer -- the first Black woman to hold the position.

This announcement brings the total number of Biden senior staff to 12: five men and eight women.

-ABC News' Molly Nagle

The Michigan board of state canvassers will convene at 1 p.m. ET Monday to certify to election results.

By state law and historically by practice, certification by the board of state canvassers -- which is made up of two Democrats and two Republicans -- is a procedural step.

The board is obligated to confirm the election results per state law -- essentially validating that the unofficial results match the tabulated votes. If the board is deadlocked, a court would likely intervene and compel certification.

All 83 counties in Michigan have certified their results, including the contested Wayne County, according to the secretary of state. The state bureau of elections also submitted a formal recommendation to the canvassing board, not only confirming Biden's victory in the state but also assuring that the errors in reporting, which Trump and his allies have exploited, are "all attributable to human error," "did not affect the actual tabulation of votes" and "were identified and corrected either prior to or during the county canvass."

While Republicans, including RNC Chair Ronna McDaniel, have called for a delay in certification to conduct an audit of Wayne County's results, the secretary of state already confirmed plans for a post-election audit, including a performance audit in Wayne County. Under current state law, audits can only be completed after the results are certified.

Biden's margin of victory in Michigan is currently more than 154,000 votes, nearly 15 times Trump's margin in 2016.

-ABC News' Kendall Karson