Sen. Patrick Leahy, who will preside over former President Donald Trump's impeachment trial, was released from the hospital on Tuesday night after not feeling well early in the evening, his office said in a statement.

"The Capitol Physician suggested that Senator Leahy go to George Washington University Hospital this evening for observation, out of an abundance of caution," Leahy spokesman David Carle said late Tuesday. " After getting test results back, and after a thorough examination, Senator Leahy now is home. He looks forward to getting back to work. Patrick and Marcelle deeply appreciate the well wishes they have received tonight."

Leahy was back presiding over the Senate Wednesday. 

A statement earlier in the evening announcing that Leahy had been taken to the hospital said that "Senator Leahy was in his Capitol office and not feeling well" but that he was taken to the hospital "[o]ut of an abundance of caution."

The 80-year-old Vermont Democrat is the longest-serving senator and the fifth-longest serving senator of all time. As Senate president pro tempore, he is third in line for the presidency after Vice President Kamala Harris and House Speaker Nancy Pelosi, D-Calif., who is also 80. 

LEAHY EXPECTED TO PRESIDE OVER TRUMP IMPEACHMENT TRIAL INSTEAD OF CHIEF JUSTICE ROBERTS

On Monday it was announced that Leahy, as the president pro tempore, will preside over the Trump impeachment trial rather than Chief Justice John Roberts. A Senate source told Fox News that senators preside when the impeached individual is not currently the president of the United States. 

Senate Majority Leader Chuck Schumer, D-N.Y., later said on MSNBC that "it was up to John Roberts whether he wanted to preside with a president who is no longer sitting, Trump, and he doesn't want to do it."

"The president pro tempore has historically presided over Senate impeachment trials of non-presidents. When presiding over an impeachment trial, the president pro tempore takes an additional special oath to do impartial justice according to the Constitution and the laws," Leahy said Monday of his role overseeing the impeachment trial. "It is an oath that I take extraordinarily seriously."

He added: "I consider holding the office of the president pro tempore and the responsibilities that come with it to be one of the highest honors and most serious responsibilities of my career. When I preside over the impeachment trial of former President Donald Trump, I will not waver from my constitutional and sworn obligations to administer the trial with fairness, in accordance with the Constitution and the laws."

U.S. Sen. Patrick Leahy (D-VT) speaks as Senate Minority Leader Sen. Chuck Schumer (D-NY) listens during a news conference in front of the U.S. Capitol after a boycott of the Senate Judiciary Committee hearing on the nomination of Judge Amy Coney Barrett to the U.S. Supreme Court on October 22, 2020. Leahy will preside over former President Trump's second impeachment trial. (Photo by Alex Wong/Getty Images)

The person presiding over the trial will hold a limited role and is not expected to substantively affect the proceedings. Leahy later Monday said that he believes he will be able to effectively and impartially preside over the trial. 

"I’ve presided for hundreds of hours over the years... I’m up to the responsibility," he said. 

Leahy is the president pro tempore because he is the most senior member of the majority party -- while Democrats and Republicans each control 50 seats, Harris is able to break ties. Sen. Chuck Grassley, R-Iowa, was the president pro tempore when Republicans held the Senate majority. 

DEMOCRATIC SENATOR PRESIDING OVER TRUMP IMPEACHMENT TRIAL PLEDGES IMPARTIALITY DESPITE CALL TO CONVICT

House impeachment managers transmitted the article of impeachment, which accuses Trump of inciting an insurrection, to the Senate on Monday. Senators were sworn in as jurors for the impeachment on Tuesday. 

An agreement between Schumer and Senate Minority Leader Mitch McConnell, R-Ky., on how to structure the trial put off the main part of the trial until the second week in February, largely to give the Senate an opportunity to continue to work on confirming Biden administration nominees. In the meantime, both the House managers and Trump's legal team will be submitting a couple of rounds of pre-trial briefs. 

Trump almost certainly will not be convicted at the impeachment trial. Sen. Rand Paul, R-Ky., Tuesday raised a point of order about whether an impeachment trial for a former president is constitutional, and all but five Republicans said it was not. 

Former President Donald Trump speaks during a campaign rally at The Villages Polo Club, Friday, Oct. 23, 2020, in The Villages, Fla. Trump is the only president to ever be impeached twice. (AP Photo/Evan Vucci)

That argument that the Senate is not even permitted to hold a trial for an individual who is no longer in office will give Republicans a convenient reason to vote against convicting Trump -- and thus avoid angering him or his base -- while also not endorsing his post-election conduct as acceptable. 

Trump in the two months following the presidential election repeated false claims that he had won the election and that there was evidence of widespread fraud. Trump then called his supporters to Washington, D.C. for a "wild" Jan. 6, rally where he doubled down on those claims shortly before Congress was set to meet in a joint session to certify the presidential election results. 

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Trump did not explicitly call for violence, and specifically called for his supporters to march "peacefully and patriotically" to the Capitol to ask Congress to overturn his loss. But Trump and his allies on the stage used pitched rhetoric they'd been using for months, and after the rally a pro-Trump mob stormed the Capitol and ransacked the building, forcing hundreds of lawmakers and former Vice President Mike Pence into hiding. 

The former president, in the immediate aftermath of the attack, was harshly condemned by those on both sides of the aisle, with many saying he did not do enough to stop the attack as it was happening. 

But in the time since the attack, Republican anger has receded, as shown in the vote on Paul's point of order Tuesday. Even at the top of the caucus, McConnell, who previously left the door open to voting to convict Trump, joined 45 of his colleagues in saying the trial is not even permissible. It would take 67 votes in the Senate to convict Trump.

Fox News' Jason Donner contributed to this report.