The Arizona Republican said Senate Democrats were being cynical when they raised opposition to Lieberman — a close friend of McCain's — after Trump administration officials last week suggested he was one of the front-runners

"My Democratic colleagues clearly did (kill Lieberman's chances)," McCain told reporters Wednesday. "This is their nominee for vice president of the United States. If anything would make you cynical about this town, that's it."

Lieberman was in fact the Democratic vice presidential nominee in 2000. But the former Connecticut senator became an independent in 2006 after losing his Democratic primary, and endorsed McCain for president in 2008 — angering many Democrats — and McCain had considered him a potential VP nominee for the Republican ticket.

Lieberman was one of the so-called "three amigos" in the Senate along with McCain and South Carolina Republican Sen. Lindsey Graham.

Further complicating Lieberman's chances to win Senate confirmation had he been selected, Lieberman is partners at the same law firm as Marc Kasowitz, an attorney Trump is expected to hire as part of a team on matters related to the special counsel probe into his campaign's alleged connections to Russia.

Sen. Ben Cardin, a Maryland Democrat, said that disqualified Lieberman.

"It would be hard to see an associate of the law firm that just was hired by the President to defend him, or to represent his interests is a better way of saying it," Cardin said. "So, yes, I think it disqualifies him."

Even before Kasowitz was named as an expected attorney for Trump, Lieberman faced problems with Democrats as a former politician who did not have law enforcement experience, as many Democrats have called for a career-FBI official to be the next FBI director.

"I think what most of us are looking for in a nomination is someone who has broad experience in the Department of Justice, the FBI, a career-type person that doesn't bring any political concerns one way or another," Cardin said. "That's what we think would be the best so we can get the type of traditional confirmation votes that would be near-unanimous that would be in the best interest of the morale of the FBI, of the Department of Justice and of the ongoing investigation."