Reince Priebus accused MSNBC host Rachel Maddow of being involved in a conspiracy, after she interviewed Lev Parnas on Thursday.
Joe Scarborough said that history will reflect poorly on Republican senators in Trump's impeachment trial, if they do not provide a fair one.
The show's previous record was 4.13 million viewers in March 2017.
In the second installment of his interview with MSNBC's Rachel Maddow, Lev Parnas compared President Donald Trump to a "cult leader," saying "There's a lot of Republicans that would go against [Trump]."
Lev Parnas told Rachel Maddow that the only reason former U.S. ambassador Marie Yovanovitch was removed from office was that she stood in the way of the Biden investigation. Parnas also said that Robert Hyde, suspected of keeping tabs on Yovanovitch's location, was "drunk all the time."
New Jersey Senator Cory Booker told Rachel Maddow he suspended his 2020 presidential campaign because of low campaign funds and his missing the last debate, a situation he called a "perfect storm."
"The Republicans in the Senate are by and large zombies, walking along as Donald Trump obliterates things like truth," Wallace said.
Having served as an adviser both George W. Bush and John McCain, Steve Schmidt left the Republican party in 2018 calling it "fully the party of Trump."
Declaring that President Trump "lies about everything all the time," MSNBC host Chris Hayes says that he wants proof that Iranian General Qassem Soleimani was planning an attack on American forces in the region.
Secretary of Defense Dr. Mark T. Esper told MSNBC's Andrea Mitchell that Iran should be a "normal country" and stop engaging in what he referred to as "bad behavior."
Former federal prosecutor Cynthia Alksne said Thursday on MSNBC that President Donald Trump's personal lawyer Rudy Giuliani lacked the "attention to detail" needed to defend Trump in an impeachment trial.
Joe Scarborough's remarks came after Kim Jong Un asserted this week that North Korea "will never" denuclearize.
"The worst thing president Trump is doing is he's calling into question the chain of command's commitment to the rule of law. He's got to knock that off," retired General Barry McCaffrey said on MSNBC.
Ending his boycott of MSNBC, Democratic presidential candidate Andrew Yang told Chris Hayes that he would "never do anything to increase the chances of Donald Trump becoming president again or staying president."
Chris Hayes also said GOP Sen. Lisa Murkowski exposed a "real crack" among Senate Republicans over the impeachment trial process.
A reporter for The Washington Post said in an opinion article on Thursday that MSNBC host Rachel Maddow "rooted" for the now mostly-debunked Steele dossier to be true during her coverage of Donald Trump's alleged collusion with Russia during the 2016 presidential election.
Joe Scarborough said that some Christian preachers were demonstrating that staying in Trump's good graces was more important than staying true to their faith.
"Whether it's Mulvaney, Bolton, Giuliani, Pompeo—if they have to testify under oath, he has to leave," former White House Communications Director Anthony Scaramucci said on MSNBC.
"During that sham trial, Pontius Pilate afforded more rights to Jesus than Democrats afforded this president in this process," Congressman Barry Loudermilk argued Wednesday.
Laurence Tribe, a Harvard Law professor and author, said on MSNBC that if Trump's requests of the Ukrainian government and his refusal to comply with subpoenas are not reason enough for impeachment, "then nothing is."
Representative Zoe Lofgren, 71, has seen three impeachment inquiries in her time at Congress. She said the articles submitted against President Donald Trump are "supported by the evidence and should be approved."
"This is really a collision between order and rule of law," former NATO Supreme Allied Commander James Stavridis said.
The attorney general touted an "important watershed moment" by the summer in the Durham investigation into the FBI.
"We know Barr will do anything for Donald Trump," Joe Scarborough said, describing William Barr as the president's "hack."
The House is likely to impeach President Donald Trump but whether the GOP-controlled Senate will convict him is an open question.
Elizabeth Holtzman was on the House Judiciary Committee that adopted articles of impeachment against President Richard Nixon.
The former senior official in the Obama and Clinton administrations said there "are no grown-ups" left in President Donald Trump's White House.
"This is the most desperate defense," Joe Scarborough said.
The call records of President Donald Trump's lawyer were released in the House Intelligence Committee's impeachment report.
Lance Dodes told MSNBC that Trump "tells other people that they are what he is."