Sen. Jeff Flake Jeffrey (Jeff) Lane FlakeHow fast population growth made Arizona a swing state Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Republican former Michigan governor says he's voting for Biden MORE (R-Ariz.) has a “credibility problem” with his calls to protect special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE, according to former Ohio state Sen. Capri Cafaro (D).

“I would have more faith in the guy if he actually voted the way he spoke,” Cafaro told Hill.TV co-hosts Krystal Ball and Saagar Enjeti on Thursday in response to a question about Flake’s demands over a bill designed to protect Mueller.

Flake, who's retiring in early January, said Wednesday that he will oppose President Trump Donald John TrumpBiden on Trump's refusal to commit to peaceful transfer of power: 'What country are we in?' Romney: 'Unthinkable and unacceptable' to not commit to peaceful transition of power Two Louisville police officers shot amid Breonna Taylor grand jury protests MORE’s judicial nominees until the Senate votes on the Mueller bill. His threat will block the Senate Judiciary Committee from approving judicial nominations and sending them to the full Senate without help from Democrats.

Republicans hold an 11-10 majority on the panel and many of the most controversial nominees are advanced along party lines, meaning they would need either Flake's vote or a Democratic senator to flip.

The bipartisan Mueller bill has been in limbo ever since it the Senate Judiciary Committee advanced the measure in April.

Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellFEC flags McConnell campaign over suspected accounting errors Poll: 59 percent think president elected in November should name next Supreme Court justice Mark Kelly: Arizona Senate race winner should be sworn in 'promptly' MORE (R-Ky.) blocked Flake's request to force a vote on the bill. McConnell argued that the special counsel is not in danger of being fired, even though President Trump has repeatedly attacked the Mueller's Russia probe, calling it a "witch hunt."

Trump on Thursday called the investigation “a witch hunt like no other in American history.”

Cafaro said that while it's helpful that Flake is putting pressure on his fellow Senate Republicans, he is grandstanding with threats that are just an act.

“I think it gives him comfort because there’s been controversy surrounding will-they-or-won’t-they kill the Mueller investigation,” she said. "But I think with Jeff Flake, he has a credibility problem because he talks a big game and then he doesn’t vote the way that he talks."

Flake has served in the Senate since 2013. His retirement has sparked speculation of a potential 2020 challenge against Trump.

Cafaro said Flake and Ohio Gov. John Kasich (R), another potential 2020 contender, don't stand a chance with Republican voters.

“He’ll get smoked – so will [John] Kasich – just simply because I think the primary electorate doesn’t have the appetite,” she told Hill.TV.

— Tess Bonn