WASHINGTON — The lengthy defense of the Biden family by House Democrats during President Donald Trump’s impeachment trial opened the door to probing whether Joe and Hunter Biden were involved in corruption in Ukraine, the defense team says.

A source on Trump’s legal team told reporters Friday that “it became quite apparent yesterday from the House managers that they’ve made it very relevant to the case, that they spent a lot of time bringing the Bidens into this case and have established that there is something relevant that’s there.”

The source said “we’ll have to be addressing that since they opened that up.”

Trump attorney Jay Sekulow told reporters late Friday that “for whatever reason, the House managers decided to not just open the door, but kick the door down on the Burisma-Biden matter. For the life of me, I’m trying to figure out what their strategy is.”

Democrats blasted Trump on Thursday as not truly concerned about corruption when he stalled nearly $400 million in foreign aid. They argued Trump wanted Ukraine to launch a probe of debunked claims against the Bidens rather than look at genuine corruption.

Trump’s defenders said the assertion requires a rebuttal when Trump’s defense arguments begin Saturday.

“I think they should tear apart the narrative presented by the House managers — this has been debunked,” said Sen. Lindsey Graham (R-S.C.).

Sen. John Kennedy (R-La.) said he believes Joe Biden’s presidential candidacy may have been incidental to Trump’s request that Ukraine investigate his son’s $50,000-a-month gig on the board of Ukraine energy firm Burisma, despite having no relevant experience, while his father was vice president and the Obama administration’s point person on Ukraine policy.

“Was he asking for an investigation of a political rival? Or was he asking for an investigation of possible corruption by someone who happens to be a political rival? There’s a big difference,” Kennedy said.

Kennedy added: “What did Hunter Biden do for the money?”

Members of Trump’s ceremonial defense team of House Republicans asserted Friday that the Bidens’ conduct is significant. “The fact that they would want to plant that red debunked stamp over it is insane,” said Rep. Lee Zeldin (R-N.Y.).

Hunter Biden was paid “$50,000 a month solely because he was Vice President Joe Biden’s son,” Zeldin said. “If it’s not illegal, it should be. So the president has a duty, whether it’s President Trump or any other president in his place, to be concerned about corruption.”

Rep. Mark Meadows (R-N.C.), said, “I’m sure Hunter Biden’s name will come up as the defense team addresses corruption more broadly.”

Countering the Democratic narrative, White House officials circulated material Thursday about Hunter Biden’s work for Burisma.

“A number of witnesses [in House impeachment hearings] raised concerns about a potential conflict of interest with Hunter Biden’s position with Burisma,” a White House official said in an email to reporters.

The official pointed to former White House Russia adviser Fiona Hill’s testimony that there was a “perception of a conflict of interest” around his role, to State Department official George Kent’s similar testimony about a “perception of a conflict of interest,” and to White House Ukraine policy adviser Alexander Vindman’s testimony that Hunter Biden did not seem qualified to serve on the company’s board.

“Burisma Used Hunter Biden to Gain Access,” a White House official said in a different Thursday blast to reporters, highlighting a report that a consulting firm was using the younger Biden’s employment “to help repair Burisma’s tarnished image.”

In a July 25 phone call that sparked his impeachment, Trump asked Ukraine’s president to investigate Joe Biden forcing the ouster of a prosecutor who had investigated Burisma, using as leverage $1 billion in U.S. loan guarantees. He also asked for a review of the whereabouts of a Democratic computer server allegedly hacked by Russia.

Democrats presenting the impeachment case against Trump counter that he wasn’t truly interested in corruption.

Rep. Sylvia Garcia (D-Texas) asserted that neither of the Bidens did anything wrong and that “there is simply no evidence, nothing, nada in the record to support this baseless allegation.”

Fellow impeachment manager Rep. Adam Schiff (D-Calif.) said, “The evidence is consistent. It establishes clearly that President Trump did not care about corruption, to the contrary he was pursuing a corrupt aim.”

Sen. Josh Hawley (R-Mo.), who wants to call Hunter Biden as a witness, said “House Democrats argued over and over that President Trump could not possibly be interested in corruption in Ukraine … What’s the evidence for that? Because Hunter Biden wasn’t involved in any corruption in Ukraine.”

“House Democrats have really hinged a key part of their case on that, and they are asking us to give no evidence, just to accept that of course there was no corruption,” Hawley said.