The White House and congressional Republicans have seized on the lack of witnesses with firsthand knowledge of President Trump’s actions on Ukraine to try to undermine the case for impeachment, a gambit that Democrats argue could backfire as more witnesses come forward.

Trump administration officials and GOP lawmakers are arguing that career diplomats testified that they never spoke directly to Trump — and therefore cannot say with confidence that he tried to strong-arm a U.S. ally into doing him political favors.

“Their understanding, which is the foundation of the case for the Democrats, was based on secondhand information,” House Minority Leader Kevin McCarthy (R-Calif.) told reporters Thursday, referencing the two witnesses at the first open impeachment hearing Wednesday.

The strategy, however, is extremely risky for the president and the GOP. While it is true that the diplomats testified that they were told by others that Trump pressured Ukraine, a witness with firsthand information — Lt. Col. Alexander Vindman, who was on the Trump call — is scheduled to testify next week. And former national security adviser John Bolton also could talk to investigators.

Additionally, if Republicans were so concerned about secondhand accounts, Democrats say, they should allow Trump associates who do have firsthand information — acting White House chief of staff Mick Mulvaney and Energy Secretary Rick Perry, for example — to testify, rather than blocking them. The White House has no plan, however, to do that, according to a senior administration official who spoke on the condition of anonymity to talk frankly.

“If you don’t like hearsay, release the documents; if you don’t like hearsay, let people testify!” said Rep. Mike Quigley (D-Ill.). “They’re afraid of the testimony they have already seen, and there’s a reason that they don’t want the rest of this to get out.”

The new talking point drastically raises the stakes for next week’s hearing with Ambassador to the European Union Gordon Sondland, who told at least four Trump officials that the president personally oversaw the entire operation. On Friday, David Holmes, the top political affairs officer at the U.S. Embassy in Ukraine, is scheduled to testify behind closed doors about a July 26 conversation he overheard between Sondland and Trump about the investigations Trump was demanding from Ukraine.

Sondland, however, told lawmakers that he never talked to Trump about leveraging military aid and a head of state meeting with Ukraine on a promise to investigate Hunter Biden, son of former vice president and 2020 presidential candidate Joe Biden, a major discrepancy he will be pushed to clear up next week.

Sondland’s testimony could be damaging for Trump should he confirm his contacts with the president, Democrats say. It could also undermine their case should he deny Trump’s involvement.

“Let me say to my friends about hearsay … the case is being built,” warned Rep. Sheila Jackson Lee (D-Tex.). “These were the two first witnesses. … Next week Ambassador Sondland will be asked and he will have to answer: ‘Were you on that call? What was said on that call?’ Under oath.”

The GOP’s strategic decision to focus on “secondhand” accounts was evident during testimony Wednesday from William B. Taylor Jr., the acting ambassador to Ukraine, and George Kent, the deputy assistant secretary of state responsible for Ukraine. Republicans, who have been scrambling for weeks to coalesce around a unified defense strategy, quickly realized that framing Trump’s request for investigations as an attempt to root out corruption were not breaking through, according to Republicans who spoke on the condition of anonymity to speak frankly.

But Republicans argued that their questions scrutinizing the witnesses’ links to Trump — led by Rep. Jim Jordan (R-Ohio) and seconded by Rep. Michael R. Turner (R-Ohio) — were more effective.

“Since you learned it from others, you could be wrong?” Turner pressed Taylor, who testified that he heard about Trump’s involvement from Sondland. “They could be wrong, or they could be mistaken or they could have heard it incorrectly, right?”

Taylor acknowledged it was possible: “People make mistakes.”

Rep. Douglas A. Collins (R-Ga.), who is not a member of the House Intelligence Committee, took to Twitter during the hearing for a bit of amplification. He posted a scene from the 1986 movie “Ferris Bueller’s Day Off” in which a character explains the protagonist’s absence from class: “My best friend’s sister’s boyfriend’s brother’s girlfriend heard from this guy who knows this kid who’s going with the girl who saw Ferris pass out at 31 Flavors last night.”

“A live look into Ambassador Taylor’s testimony in the Schiff impeachment proceedings,” Collins wrote.

The White House also embraced the “secondhand information” talking point. On Wednesday night, White House press secretary Stephanie Grisham argued on Fox News that “the two star witnesses couldn’t even say that they’ve ever met the President.” The RNC likewise put out a video of Taylor testifying about how he can only speak to what others have told him about Trump’s involvement.

“Democrats’ star witness: ALL HEARSAY,” the RNC video said.

The talking point has clearly struck a nerve for Democrats, who have scoffed in recent weeks at Republicans’ inability to explain Trump’s actions in defending the president. Asked about the GOP argument at a news conference Thursday, House Speaker Nancy Pelosi (D-Calif.) warned a reporter, “Don’t fall into the secondhand stuff.”

“That is such a fraudulent proposition put forward by the Republicans,” Pelosi said, later accusing Trump of “bribery,” a fresh Democratic talking point that could be an article of impeachment. “That is such a fraudulent proposition, and they know it.”

Privately, however, Democrats say the argument could be problematic if it resonates with independent voters. They’re already working to combat the talking point by highlighting Trump’s request in a July 25 call that Ukraine President Volodymyr Zelensky “do us a favor” and investigate the Bidens, holding it up as evidence of his own involvement.

Democrats also point out that Trump’s personal lawyer Rudolph W. Giuliani has, by his own admission, pressured Ukraine to commit to the probes — and said he did it on behalf of his client in the Oval Office. Mulvaney acknowledged a quid pro quo at a news conference, though he later walked it back.

“If they’re concerned about secondhand information, go read the readout of the call on July 25. Replay what Mulvaney said at his press conference. And then go read the testimony of the witnesses,” said Rep. Val Demings (D-Fla.), an impeachment investigator and former police detective.

Demings argued that “many of the best cases involving criminals engaged in criminal behavior were made based on second- and third-hand information.”

“What we have to do is look for corroborating information that supports it,” she continued. Taylor and Kent “may not have ever talked to the president directly, but they daggone sure talked to people who talked to the president directly.”

The GOP assessment, however, has resonated with at least one centrist Democrat. Rep. Jeff Van Drew (N.J.), one of only two Democrats to vote against impeachment inquiry rules in late October, told CNN that Taylor’s testimony was “hearsay” just hours after the blockbuster hearing.

“It’s really difficult dealing with this because it’s he said-she said,” he said.

In many respects, the witnesses being dismissed by Republicans do have firsthand knowledge that is extremely relevant and, Democrats argue, still makes the case that Trump abused his power and should be impeached. Taylor and Kent, for example, were able to speak firsthand about how a shadow campaign run by Giuliani and Sondland derailed traditional U.S. policy toward Ukraine, subverting American national interests in favor of leveraging probes of Trump’s adversaries.

Additionally, Taylor, former top Russia adviser on the National Security Council Tim Morrison and former U.S. special envoy to Ukraine Kurt Volker have all testified that Sondland told them he spoke with Trump, and that the president personally wanted military aid or plans for a head of state meeting halted until Ukraine made a public commitment to investigate the Bidens.

If Sondland continues to deny such conversations, Democrats argue that Americans will believe their witnesses — apolitical State Department employees who have served presidents of both parties — over the word of the Trump ally who has already been forced to amend his testimony. Sondland initially denied the existence of a quid pro quo over military aid.

But after Taylor and Morrison testified that Sondland had told them that he informed Ukrainian officials they would get no money without the probes, Sondland changed his testimony and admitted delivering the message.

Republicans, meanwhile, are privately gearing up to discredit Sondland if he confirms the exchanges with Trump. They plan to argue he is not a credible witness because he has changed his testimony, according to Republicans who spoke on the condition of anonymity to describe private deliberations.

Democrats also think they can hit Republicans for blocking what they view to be firsthand accounts as well.

“[Trump’s] counsel sent a eight-page letter saying no witnesses, no documents, no nothing — and now the Republicans are arguing we don’t have documents or witnesses,” said Rep. Peter Welch (D-Vt.), an impeachment investigator who hopes the public will notes the contradiction. “Desperate times call for desperate measures and they’ve got desperation when it comes to addressing the factual elements of this, so they’re doing everything they can to distract.”