President TrumpDonald John TrumpDem senator says Zelensky was 'feeling the pressure' to probe Bidens 2020 Dems slam Trump decision on West Bank settlements Trump calls latest impeachment hearings 'a great day for Republicans' MORE’s congressional allies and critics on Sunday doubled down on their respective positions on the impeachment inquiry as the House prepares to move into the public phase of the process.

Which witnesses should appear was a key topic after House Intelligence Committee ranking member Devin NunesDevin Gerald NunesThe Memo: GOP plays risky game with attacks on Vindman Five things to know about Tuesday's impeachment hearings Nunes complains Democrats adding extra time for questioning witnesses MORE (R-Calif.) requested that former Vice President Joe BidenJoe Biden2020 Dems slam Trump decision on West Bank settlements Trump calls latest impeachment hearings 'a great day for Republicans' Overnight Health Care: GOP senator says drug price action unlikely this year | House panel weighs ban on flavored e-cigs | New York sues Juul MORE’s son Hunter Biden be called to testify. Republicans also plan to call the whistleblower whose complaint helped spark the inquiry, among others.

Rep. Sean Patrick Maloney (D-N.Y.), a member of the Intelligence Committee, said that while some of the suggested Republican witnesses would likely be called, he saw no reason to have Hunter Biden as a witness.

“He has no knowledge of what the president did or didn’t do … there are certainly questions but it isn’t relevant to this week’s hearing,” Maloney said on “Fox News Sunday.”

Sen. Amy KlobucharAmy Jean Klobuchar2020 Dems slam Trump decision on West Bank settlements Sanders official predicts health care, climate change will be top issues in fifth Democratic debate Key Republicans say Biden can break Washington gridlock MORE (D-Minn.) expressed similar sentiments, telling CNN’s Jake TapperJacob (Jake) Paul TapperLawmakers spar over upcoming Sondland testimony Murphy: Sondland has to decide if his loyalty is to America or Trump House Intelligence Republican: Trump Yovanovitch tweet 'not witness intimidation' MORE, “I have seen no reason why you would have Hunter Biden testify when from all the reports we’ve seen is that this is not a valid investigation.”

Democrats also indicated they were confident in their position going into public hearings, saying the depositions that have been released of closed-door sessions show evidence of impeachable offenses. 

Rep. Jackie SpeierKaren (Jackie) Lorraine Jacqueline SpeierMaloney wins vote for Oversight chairwoman Live coverage: House holds third day of public impeachment hearings Sondland testimony looms over impeachment hearings this week MORE (D-Calif.), meanwhile, said the inquiry thus far demonstrated a “very strong case of bribery.”

“Because you have an elected official, the president, demanding action of a foreign country in this case, and providing something of value, which is the investigation, and he is withholding aid, which is that official act,” she said on ABC’s “This Week.” “And the Constitution is very clear: treason, bribery or acts of omission. In this case, it's clearly one of those.”

And Rep. Eric SwalwellEric Michael SwalwellThe Hill's 12:30 Report — Presented by Johnson & Johnson — Vindman defends witnesses from 'cowardly' attacks at third day of hearings Swalwell on flatulence allegation: Total exoneration Trump attacks Pence aide who called Ukraine call 'inappropriate' MORE (D-Calif.) said on CBS’s “Face the Nation” that closed-door depositions had already shown evidence of an “extortion scheme” on the part of the White House.

However, Swalwell added, “It’s important that these witnesses raise their right hands and take questions from both Republicans and Democrats. … It’s important that the Republicans are afforded the opportunity to suggest which witnesses we should call and we’ll decide whether that’s relevant.”

On the Republican side, Rep. Will HurdWilliam Ballard HurdImpeachment hearings likely to get worse for Republicans The Hill's 12:30 Report: Democrats open televised impeachment hearings Here are the key players to watch at impeachment hearing MORE (Texas), a former CIA officer, broke with some of his colleagues by defending the whistleblower's right to anonymity.

“I think we should be protecting the identity of the whistleblower … because how we treat this whistleblower will impact whistleblowers in the future,” Hurd told Fox’s Chris WallaceChristopher (Chris) WallaceChris Wallace: Trump testifying 'would be akin to Prince Andrew testifying about his relationship with Jeffrey Epstein' Fox's Neil Cavuto rips into Trump over attacks on Chris Wallace's impeachment coverage Trump rips 'nasty' and 'obnoxious' Chris Wallace after he presses Scalise about impeachment MORE on “Fox News Sunday."

However, Hurd backed up Nunes’s call for Hunter Biden to testify.

“I think we should just turn over every rock and pursue every lead,” Hurd said.

“I would like to hear from Hunter Biden — I would love to hear from the other Americans who served on the board of Burisma,” he added, referencing the Ukrainian natural gas firm upon whose board the younger Biden served.

Sen. John KennedyJohn Neely KennedyMORE (R-La.) conceded that, depending on intent, Trump’s pressure on Ukrainian President Volodymyr Zelensky to investigate the Bidens could have been “over the line.”

“Here are two possible scenarios: number one, the president asked for an investigation of a political rival, number two, the president asked for an investigation of possible corruption by someone who happens to be a political rival,” Kennedy said on CBS’s “Face the Nation.”

“The latter would be in the national interest, the former would be in the president’s parochial interest, which would be over the line,” he added.