Retired Brigadier General Peter Zwack, who was once Vindman's supervisor, said he "always had a lot of respect" for Graham.
"I don't know what happened to Lindsey," the former vice president's wife said.
The indicted Florida businessman told CNN he did not know if Graham was "deeply involved" and had not had direct contact with the senator.
Senator Lindsey Graham said on Twitter Monday that evidence against former Vice President Joe Biden and his son Hunter had not been disproven. "They most definitely should not be swept under the rug," Graham tweeted.
In an effort to make their impeachment case against President Donald Trump, House Democrats, specifically Jerry Nadler of New York used a 1999 video of then-Representative Lindsey Graham, which goes against his recent arguments defending Trump.
House impeachment managers use Republicans' words from the past to dispel the notion that a president cannot be impeached for acts that do not amount to crimes.
Graham—a loyal supporter of President Donald Trump—was pictured praising the Democratic impeachment manager and shaking his hand.
Senator Lindsey Graham reacted to claims that the GOP were "covering up" for Trump at the Senate impeachment trial by insisting that he was instead exposing Democratic "hatred."
Biden also criticized senators Elizabeth Warren and Bernie Sanders for being unable to inspire Democratic voting down the ticket.
"That directly contradicts what you said as a Republican House impeachment manager in 1999 during the Clinton impeachment trial," Chris Wallace noted.
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 South Carolina congressman said new evidence presented by Parnas was "no different" to earlier impeachment evidence.
The GOP senator said Nancy Pelosi "gave in" to Mitch McConnell, and that the "dangerous" Senate impeachment trial will end in days, not weeks.
Democrats are keen to hear from key administration official witnesses, but Republicans led by Senator Mitch McConnell are fighting the proposal.
"Senator, some of us still respect the Constitution and understand our role in Congress isn't to bow or kiss the ring of the President," Ilhan Omar told Lindsey Graham.
"Hats off to Mitch McConnell for playing this very well. We'll take the trial up next week," Graham said.
While appearing on Tuesday's edition of Hannity, Senator Lindsey Graham also declared that "America first means to me now more than anything else, you kill an American, you're going to be the first we come after."
A 1999 video showed then-Representative Lindsey Graham stating the need for witnesses during Bill Clinton's impeachment trial.
"AOC doesn't know anything about the law of armed conflict, obviously," Graham said.
"And to my Democratic colleagues: Every commander in chief has the inherent authority to protect our troops in the field. He had all the authorization he needs," Graham said during an appearance on 'Hannity' Friday.
Friday on 'Fox & Friends,' Senator Lindsey Graham said that U.S. forces should target oil fields and refineries in Iran, not Iraq or Syria, calling them "economic targets that would crush the economy."
Alaska Republican Senator Lisa Murkowski said she was "disturbed" after hearing Senate Majority Leader Mitch McConnell and other top GOP senators were coordinating the impending impeachment trial with the White House.
Glenn Kirschner wrote that Americans should be wary of the "drug deal" the senators may be "cooking up."
Lindsey Graham on Sunday accused Pelosi of playing "with a dead cat" and condemned the Democrat-led House for aggressively pursuing impeachment.
"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.
"These are nominees that we're seeing who are not just inimical to LGBT protections but to civil rights generally," a senior attorney with Lambda Legal said.
A new poll about the impeachment of President Donald Trump shows most people think he will be well treated by the GOP-controlled Senate.
Rep. Zoe Lofgren told MSNBC that it is bad for President Donald Trump if people suspect his Senate trial is rigged because it would undermine any claim of exoneration.
The South Carolina Republican told "Face the Nation" that President Trump should "get out of the way" when somebody was ready to acquit him.
"I think it is the responsibility of the American people to hold these senators accountable," the congresswoman from Minnesota said.