There is a preliminary plan to close the entire National Mall to the public for Inauguration Day amid security concerns, ABC News has confirmed.

The Washington Post was the first to report on the development, but The National Park Service has said it will make an announcement on the Mall following ongoing discussions with the Secret Service, the Biden Inaugural team and D.C. Mayor Muriel Bowser.

Traditionally, members of the public gather on the National Mall -- bookended by the Capitol building and Lincoln Memorial -- for viewing of the inauguration on large jumbotrons.

But the Mall's potential closure comes in the wake of a violent seige on the U.S. Capitol building last week, which left at least five people dead, and amid heightened security concerns regarding armed protests being planned ahead of Biden's inauguration on Jan. 20.

Security preparations for next week have already increased with up to 20,000 National Guard troops authorized to provide security at the Capitol and around Washington, D.C., for next week's ceremony, according to a Defense Department official.

Bowser has already warned visitors to stay away from the District for the inauguration due to threats of both the coronavirus pandemic and of violence.

Editor’s Note: A previous version of this post reported that the entire National Mall would be closed to the public for Inauguration Day amid security concerns. The text has been updated to reflect the fact that the closure is only a preliminary plan.

-ABC News' Dee Carden and Josh Margolin

Arizona Gov. Doug Ducey, a Republican, has announced he will attend Biden’s inauguration after weeks of attacks from Trump for signing the certification of Arizona's election results affirming Biden's narrow win in the state.

“It doesn't matter who you supported in the election — once the election is over, we put country before party. Never has it been more important than right now to observe these traditions for the whole world to see," Ducey said in a statement Thursday.

"I was honored to represent Arizona at the inauguration of President Trump in 2017, and I am honored to represent our state at the 59th Inaugural Ceremonies next week. President-elect Biden is assuming office at a critical time in our nation’s history, and I wish him well," he added.

The Arizona Republican Party is scheduled to meet a few days later on Jan. 23, when members will vote on censuring some apparent party foes including Ducey, Cindy McCain and former Sen. Jeff Flake, R-Ariz.

-ABC News' Meg Cunningham

On one side of Pennsylvania Avenue in Washington, D.C., President Trump -- now the only president in history to be impeached twice -- faces another Senate trial following the House charging him Wednesday with one article of impeachment for "incitement of insurrection." Shortly after 10 Republicans sided with Democrats for the vote, Trump released a video from the Oval Office condemning the violence at last week's Capitol riot, which he called a "calamity," but he did not address impeachment.

On the other side of Pennsylvania Avenue stands what's now become a crime scene -- the U.S. Capitol complex. By this weekend, up to 20,000 National Guard troops, many armed, will be deployed to the area amid heightened security concerns and ahead of Biden’s inauguration. Inside the Capitol, metal detectors were installed to enter House chamber earlier this week, and House Speaker Nancy Pelosi announced plans to fine members who don't comply with the new protocol up to $5,000.

Senate Majority Leader Mitch McConnell signaled Wednesday that Trump's Senate trial should take place after Trump leaves office, saying he wouldn't call back the Senate ahead of its Jan. 19 return. McConnell also indicated Wednesday he's considering voting to convict the president, issuing a statement that says he has "not made a final decision." Pelosi has not publicly announced her timeline, but a source involved with deliberations told ABC News Wednesday she plans to send the article to the Senate next week.

Biden, reacting to Trump’s second impeachment late Wednesday, expressed his hope that the Senate will be able to maintain a bifurcated schedule, allowing the trial to move forward along with his agenda -- a message his transition has been consistent on this week. But Democrats are facing the reality that Trump is still likely to loom large over Biden's first days in office.

On Thursday evening, Biden is slated to deliver remarks on the public health and economic crises from Wilmington, Delaware, and introduce his COVID-19 vaccine and economic relief proposal. Vice President-elect Kamala Harris is expected to join.

There are no public events on Trump’s schedule.

With Trump facing a Senate trial as soon as next week, he has no organized defense team as his top lawyers have refused to represent him.

White House counsel Pat Cipollone, his deputies, and outside lawyers Jay Sekulow, and Jane and Marty Raskin are not expected to be involved.

Trump has been increasingly irritated with his personal attorney Rudy Giuliani and hasn’t been taking his calls, according to sources familiar with the matter, though Giuliani has been spotted in the West Wing recently.

And former Harvard professor Alan Dershowitz is not on board yet, though aides to the president have had discussion with him about joining the team.

Another attorney, John Eastman, whose extremist positions have troubled some members of the president’s legal team recently, is expected to take some sort of role in Trump’s impeachment defense.

Eastman represented the president in the Texas dispute and has previously pushed a racist conspiracy theory about Vice President-elect Kamala Harris.

Trump has asked top aides about how a Senate trial would look this time around. As he did during his first impeachment, Trump raised the idea of testifying himself, which aides dissuaded him from pursuing.

-ABC News' Katherine Faulders and John Santucci

Democrats and Republicans are expected to debate for one hour -- equally divided between Democrats and Republicans -- before a procedural vote ahead of the chamber beginning debate on the impeachment article itself.

Democrat Rep. Jim McGovern, the chairman of the House Rules Committee, setting up that preliminary vote on the terms of the debate, called the Capitol a "crime scene" and the rioters "traitors" and "domestic terrorists" in an assault instigated by Trump, emphasizing, "We wouldn't be here if it weren't for the president of the United States."

McGovern described the day as "a ceremonial role for the Congress -- one that sends a message to the world that democracy persists -- but at a rally a mile and-a-half down Pennsylvania Avenue, Donald Trump was stoking the anger of a violent mob," he began. "He said Vice President Pence has to come through and told the mob to walk down to the Capitol."

"The signal was unmistakable. These thugs should stage a coup so Donald Trump can hang on to power, the people's will be damned. This beacon of democracy became the site of a vicious attack. Rioters chanted, 'Hang Mike Pence,' as a noose and gallows were built. Capitol Police officers were beaten and sprayed with pepper spray. Attackers hunted down lawmakers to hold them hostage or worse," McGovern continued.

"I saw evil, Mr. Speaker. Our country came under attack, not from a foreign nation but from within," he added. He also slammed Republicans for preaching unity from members who voted to overturn a free and fair election.

Republican Rep. Tom Cole -- one of the lawmakers who object to Electoral College results after the violent seige -- called Jan. 6 the "darkest day" of his long career in Washington, but said Democrats, instead of promoting unity, are looking to "divide us further" by pursuing Trump's impeachment.

Cole did not directly defend Trump's actions or rhetoric but argued in Congress, one week before Biden's inauguration, sets up a "flawed process."