Graham, speaking with Fox News's Bret Baier, said he would "look at" calling Hunter Biden to testify only if Rudy Giuliani, Trump's personal lawyer, first testified before the panel.
"I’ve asked Rudy Giuliani to come before our Senate Judiciary Committee to talk about corruption in Ukraine, and if he does come and he does tell us, then we’ll look at calling Hunter Biden," Graham said.
Graham's remark on having Giuliani appear before the Senate Judiciary Committee comes after Giuliani told House lawmakers on Tuesday that he won't comply with a congressional subpoena for documents and communications related to House Democrats' impeachment inquiry, citing a White House letter stating that it would not cooperate with the impeachment inquiry, which it claimed was invalid.
Asked about Giuliani's decision, Graham brushed it off, saying, "That's up to Rudy."
"I think this is a defining moment in the Biden campaign. Joe Biden is truly a friend. ... I think he’s a good man. But what Hunter Biden did was wrong at every level," Graham added during his Fox News interview. "I think what Hunter Biden did does not pass the smell test."
Graham had previously indicated that an individual outside Congress should investigate the Bidens and Ukraine. But in a reversal, he announced during the recess that he was inviting Giuliani to testify.
"Given the House of Representatives' behaviour, it is time for the Senate to inquire about corruption and other improprieties involving Ukraine. Therefore I will offer to Mr. Giuliani the opportunity to come before the Senate Judiciary Committee to inform the Committee of his concerns," he said in a statement last week.
House Democrats launched their impeachment inquiry on September 24 to probe whether Trump tried to pressure Ukraine into investigating his political rival, Joe Biden. Lawmakers initiated the inquiry after a whistleblower sent a complaint to Congress, saying that Trump threatened to withdraw military aid to Ukraine if Kyiv failed to probe Biden and his son Hunter Biden.
The Trump administration has said it will not cooperate with the impeachment probe because the House did not hold a formal vote to authorize the inquiry.
Trump has denied any wrongdoing and has denounced the impeachment inquiry as a witch hunt aimed at reversing the outcome of the 2016 presidential election.