Republicans' impeachment probe of President Biden is unraveling because of a lack of evidence — but their work could become the basis for federal investigations and even prosecutions of the Biden family if Donald Trump wins re-election, Axios has learned.

Why it matters: Trump has vowed retribution against his enemies if he wins in November. House Republicans have struggled to show Biden has done anything illegal, but people close to Trump are still plotting to use the Justice Department against Biden and his family.

• A source close to the Trump campaign said that "everything you have seen from the Biden DOJ," in terms of the charges against Trump, "you can expect to see from the Trump DOJ."
• One Trump ally argued that there is precedent for a second Trump administration to investigate and prosecute the Bidens: the current federal charges against Trump.

Reality check: Those charges stem from allegations that Trump led a conspiracy to try to overturn the 2020 election, and that he illegally kept classified documents and then schemed to conceal that he'd taken them.

• Biden was found to have some classified documents from his vice presidency, but cooperated with authorities in returning them.
• The special counsel who investigated Biden's case, a former Trump appointee to the Justice Department, decided not to prosecute.

Driving the news: House Republicans have alleged that Biden should be impeached because he illicitly benefitted from lucrative foreign deals arranged by his son Hunter.

• Despite their difficulty proving that, Trump has said he thinks Biden should be prosecuted anyway — because Trump is being prosecuted now.
• "By weaponizing the DOJ against his Political Opponent, ME, Joe has opened a giant Pandora's Box," Trump posted on Truth Social in January.
• House Oversight Committee chair James Comer (R-Ky.) said in a fundraising email last month that "when President Trump returns to the White House, it's critical the new leadership at the DOJ have everything they need to prosecute the Biden Crime Family and deliver swift justice."
• Comer also said on Fox News recently that if Attorney General Merrick Garland's Justice Department won't accept criminal referrals from House Republicans, "then maybe a Donald Trump Department of Justice will."

Zoom in: House Republicans' investigation is unlikely to end in impeachment articles this year, but the GOP has used it to sling mud at the president and his family in the run-up to the Nov. 5 election.

• Mike Davis, former chief counsel for nominations to then-Senate Judiciary chair Chuck Grassley (R-Iowa) — whom Trump has suggested as a possible interim attorney general — claims the Bidens participated in "illegal foreign corruption."
• "The Biden Justice Department will not do anything about it, so the Trump 47 Justice Department should," Davis said.

State of play: A spokesperson for the House Oversight Committee told Axios that "impeachment is 100% still on the table."

• The spokesperson said the investigation is ongoing and that a final report with recommendations will be released at the end of the probe.
• That report is expected to include criminal referrals.

The other side: Rep. Jamie Raskin (D-Md.), the top Democrat on House Oversight, told Axios that Republicans are eyeing this course of action only because their impeachment inquiry has not turned up any crimes committed by the president.

• "Now, in saying that they are going to enable Donald Trump's criminal vengeance campaign, they are taking this from a farce to tragedy," Raskin said.

Sophia Cai contributed reporting.