As the third day of the ongoing impeachment trial of President Trump wrapped up in the Senate chamber, most of the drama was elsewhere -- with one witness for the Democrats accusing a Republican senator of "defamation" and "slander" after she questioned his patriotism and implicated him in a scheme to take down Trump from inside the White House.

The off-field spat began Thursday evening on Twitter, when Tennessee GOP Sen. Marsha Blackburn quoted the commanding officer of Lt. Col. Alexander Vindman as saying that Vindman was a "political activist in uniform."

Vindman, a National Security Council official, testified during House Democrats' impeachment inquiry last year that Trump's Ukraine dealings left him in a state of "shock," and Democrats were quoting from Vindman's remarks during the Senate trial on Thursday. Vindman has denied knowing the identity of the whistleblower who flagged Trump's fateful July 25 phone call with Ukraine's president -- a claim that Republicans have questioned, because under cross-examination, Vindman apparently admitted to leaking the contents of Trump's call to the whistleblower.

At the time, California Democratic Rep. Adam Schiff, presiding over the House impeachment inquiry, shut down GOP attempts to press Vindman as to whom he had leaked information about Trump's call, saying it would potentially reveal the whistleblower's identity.

Blackburn tweeted as Schiff spoke on Thursday evening: "Adam Schiff is hailing Alexander Vindman as an American patriot. How patriotic is it to badmouth and ridicule our great nation in front of Russia, America’s greatest enemy? ... Alexander Vindman broke the chain of command and leaked the contents of the President’s July 25th phone call to his pal, the 'whistleblower.' Over a policy dispute with the President! How is that not vindictive?"

SCHIFF, IN MAJOR REVERSAL, ADMITS HE SHOULD HAVE BEEN CLEAR ABOUT HIS OWN CONTACT WITH THE WHISTLEBLOWER

"It makes sense that Alexander Vindman leaked the July 25th phone call to his friend (aka the 'whistleblower')," Blackburn continued. "They both have lots in common: —Held the same NSC job —Liberals who worked under Obama —Wanted to take out Trump."

The whistleblower's attorney, Mark Zaid, has openly recruited potential informants from within the intelligence community since 2017, when he declared that a "coup has started" against Trump and predicted that impeachment would follow. Zaid also attempted to solicit prominent actors to raise awareness to his efforts to oust Trump, which began years before Trump's call with Ukraine's leader that ultimately led to his impeachment. Zaid has further acknowledged that the whistleblower had contact with a prominent 2020 Democratic presidential candidate, but has not commented on specifics.

Vindman's legal team fired back within hours.

"This difficult moment in our country calls for seriousness and seriousness of purpose," David Pressman, a lawyer with Boies, Schiller & Flexner LLP representing Alexander Vindman, said in a statement obtained by Fox News. "Lieutenant Colonel Alexander Vindman has sacrificed enormously for our country. He believes in our country. And he believes in our country’s great institutions, including the United States Senate."

INGRAHAM INVESTIGATION: MORE TO UNCOVER CONCERNING BIDENS, BURISMA

Pressman added: "That a member of the Senate – at a moment when the Senate is undertaking its most solemn responsibility – would choose to take to Twitter to spread slander about a member of the military is a testament to cowardice. While Senator Blackburn fires off defamatory tweets, Lieutenant Colonel Vindman will continue to do what he has always done: serve our country dutifully and with honor."

Speaking to "The Ingraham Angle" late Thursday, Blackburn doubled down, saying that she has spoken to many members of the military who have a "problem" with the way Vindman circumvented the chain of command to try to undermine Trump's foreign policy.

"We honor the service of every man and woman in uniform," Blackburn told anchor Laura Ingraham. "You look at what his commanders said. He has a problem with his judgment. That's been pointed out. He had one commander who said he is a political activist in uniform. He has had problems with going outside of his chain of command, which is what he did here.

"I talk to a lot of military members on a regular basis," Blackburn went on. "They have a real problem with some of the things and the manner in which he conducted himself in this matter. What we want to do is make certain that we get to the heart of the issues here; we want to be certain the president is treated fairly. We want to make certain that we move through this and that we get back to the people's business, things they want to see us do, like putting more judges on the federal bench."

'COUP HAS STARTED,' WHISTLEBLOWER ATTORNEY PROMISED IN 2017 TWEETS

At one point during his impeachment testimony last year, Vindman was caught in an apparent contradiction late in the day by Republican Ohio Rep. Brad Wenstrup. Vindman testified that he did not discuss his concerns about Trump's July phone call with the NSC's Tim Morrison, his superior, because he was unavailable. But, under questioning from Wenstrup, Morrison confirmed that Vindman had given him edits of the transcript of the call, on the same day that Vindman testified Morrison was unreachable.

Morrison further testified he had heard others express concern that Vindman was a leaker, and could not be trusted with key information. Asked about that allegation, Vindman read from a glowing performance review that described him as an exemplary officer.

Meanwhile, it remained unclear whether Vindman -- or any other witnesses -- would appear at the Senate trial, with Trump attorney Jay Sekulow telling reporters he didn't expect Democrats would present a compelling enough case to justify that step, but that it was still too early to discuss the issue.

CHIEF JUSTICE ROBERTS ADMONISHES BOTH SIDES, AS FIRST DAY OF IMPEACHMENT TRIAL ERUPTS INTO SHOUTING MATCH AFTER MIDNIGHT

On the whole, senators generally seemed somewhat more alert on Thursday, the third full day of the ongoing Senate impeachment trial and the second full day of the Democrats' opening arguments in the case.

"It was a long day," Alaska GOP Sen. Lisa Murkowski, a key moderate swing vote, told Fox News as the day wrapped on Thursday. "I was one pooped puppy.”

She said she might have a glass of wine and take a bath tonight to relax. On Wednesday, Murkowski said she was "offended" when Democratic impeachment manager Jerry Nadler, D-N.Y., tried to argue that senators would be participating in a "coverup" if they opposed Democrats' document requests -- an aggressive move that apparently backfired in the chamber, and led to a rare intervention from Chief Justice John Roberts.

On his way out of the Senate on Thursday, though, Nadler said he was confident.

“I think we're making an airtight case for anyone who's willing to listen," Nadler told Fox News. "The evidence is overwhelming. The president's counsels have not offered any evidence against it, nor will they, because there is no possibility. And as I said the other day, or yesterday, watch what the president's counselors say. It won't be refutations of the evidence; there won't be any new evidence, there will just be criticisms of the House managers, of our procedures, all irrelevant to the charges against the president.”

From the Senate gallery on Thursday, senators could be seen sitting in their seats for longer periods and intently taking what appeared to be more detailed notes than they were the previous two days. Multiple senators told Fox News they believe that’s because senators are more rested today after the session on Tuesday drifted into Wednesday, before adjourning at 1:50 a.m. ET.

The day brought few new arguments, as Democrats focused primarily on the "abuse of power" impeachment article instead of the "obstruction of Congress" charge. Democrats' impeachment managers said there was no evidence that former Vice President Joe Biden did anything improper in dealings with Ukraine, and that President Trump sought a political investigation of Biden by Ukraine solely to sway the 2020 election in his favor.

"There was no basis for the investigation the president was pursuing and pushing. None. He was doing it only for his own political benefit," said Rep. Sylvia Garcia, D-Texas.

Similarly, they argued that there was no truth to the theory pushed by Trump and his allies that Ukraine meddled in the 2016 U.S. election. Although Democrats -- and some news outlets, including The Associated Press -- have repeatedly claimed that the idea of Ukraine meddling is a "conspiracy theory," a Ukrainian court has ruled that officials in the country did illegally meddle in the U.S. election. Additionally, a 2017 investigative report by Politico found extensive efforts by Ukrainians to hurt Trump's presidential campaign.

IMPEACHMENT BACKFIRE? KEY MODERATE REPUBLICAN SAYS NADLER'S AGGRESSIVE REMARKS HAVE 'OFFENDED' SENATE

"Trump put himself first," ahead of U.S. policy and the national interest, Schiff, acting as Democrats' lead prosecutor, told the Senate.

Added New York Rep. Hakeem Jeffries: "The decision to grant or withhold an Oval Office meeting with [Ukrainian] President Zelensky had serious security concerns for both Ukraine and the United States."

Yesterday, Trump and even some left-of-center commentators mocked Schiff for suggesting that Trump must be removed by the Senate because the 2020 election is already compromised. Schiff also implied Russia might invade the United States.

On Thursday, during his closing remarks, Schiff changed the argument somewhat. Invoking Vindman's statement that "here, right matters," Schiff said that Trump needed to be removed because he was "dangerous" and trusted his personal attorney over the intelligence community.

Additionally, Schiff said Trump could not be trusted in the event that Russian hackers hypothetically attempted to publicize internal documents related to potential Biden corruption.

Earlier in the day, Democrats were laughing along as Schiff joked that Trump had “made a religious man out of Vladimir Putin,'' a reference to a comment by Putin last November: “Thank God,'' he told an economic forum in Moscow, ”no one is accusing us of interfering in the U.S. elections anymore; now they’re accusing Ukraine."

"I was one pooped puppy." — Alaska GOP Sen. Lisa Murkowski

The theory that blames Ukraine for interfering in the 2016 elections is no laughing matter, Schiff said, calling it central to the impeachment charges. Trump is accused of seeking the Ukraine investigation — and a probe of Joe Biden and his son Hunter — for his own political benefit while holding back congressionally approved military aid as leverage.

SCHIFF WARNS RUSSIANS COULD INVADE THE U.S., SAYS 2020 ELECTION IS COMPROMISED SO SENATORS NEED TO REMOVE TRUMP NOW

The White House and some congressional Republicans have raised questions about Hunter Biden’s lucrative job on the board of a Ukrainian natural gas company, and Joe Biden's successful efforts to force the firing of a corrupt Ukrainian prosecutor. Biden was overseeing Ukraine policy as vice president while Hunter made big money in Ukraine, and Hunter got the job after testing positive for cocaine in the Navy Reserves.

During the House impeachment proceedings, a career State Department employee testified that he had flagged Hunter Biden's apparent conflict of interest at the time but was told essentially not to bother the vice president's office.

Sen. Lindsey Graham, R-S.C., vowed that Hunter's actions would soon play a large role in the trial.

“I know a lot about the Trump family and their dealings in Russia,” Graham said. “I don’t know anything about the Biden connection. You’re going to hear more about that.”

As senators sat through endless hours of arguments on impeachment, they found a new outlet to focus their attention: fidget spinners.

Sen. Richard Burr, R-N.C., handed out the toys to his colleagues before Thursday's trial proceedings began. A fidget spinner is a small toy designed to be spun between the fingers, relieving stress or boredom.

INSIDE THE CHAMBER, RESTLESS LAWMAKERS STRUGGLE TO PAY ATTENTION AS SENATE TRIAL DRAGS ON

Burr was seen playing with a blue spinner while listening to arguments by Rep. Jerrold Nadler, D-N.Y., an impeachment manager.

Other senators, including Sen. Tom Cotton, R-Ark., and Pat Toomey, R-Pa., were also seen with spinners on their desks.

While senators are pledged to silence during the trial proceedings — and deprived of their phones and other electronics — they are speaking out during breaks in the action.

Senate Minority Leader Chuck Schumer, D-N.Y., meanwhile, rebutted Republican senators who lamented they heard nothing new from House prosecutors. Republicans voted nine times this week to block the Democrats' proposed amendments for new witnesses and documents.

“If they want new stuff, there is plenty of it,'' Schumer said at a news conference before Thursday's session. ”As the [impeachment] managers made clear, a lot of the documents are sitting there, all compiled, all ready to go, with simply a vote of four Republicans to subpoena them.''

CLICK HERE TO GET THE FOX NEWS APP

Democrats are expected to wrap up their arguments when the proceedings resume at 1 p.m. ET Friday, with Trump's legal team set to make its case for up to three days beginning Saturday. Sekulow deflected rumors that the defense may wrap up in a single day.

“We're going to use a sufficient amount of time to defend our case and point out the inconsistencies of their case. We're not going to run out the clock,'' he said. ”I am confident that whether it is [completed] Saturday or Monday or Tuesday that the case will be made defending the president. I have no doubt.''

Fox News' Chad Pergram, Marisa Schultz, Caroline McKee, Mike Emanuel, Thomas Firth, Andrew O'Reilly, Jason Donner, and Adam Shaw contributed to this report, as well as The Associated Press.