Former VP Joe Biden pushed back Thursday against allegations from President Trump, saying he had never profited from foreign sources. "Nothing was unethical," Biden told debate moderator Kristen Welker about his son Hunter's work in Ukraine while he was vice president.

Why it matters: The Trump campaign is seeking to use recent allegations that Biden was involved in his son's foreign business dealings to paint the former vice president as corrupt. Earlier on Thursday, Hunter Biden's former business partner, Tony Bobulinski, released a statement saying Joe Biden's claims that he never discussed overseas business dealings with his son were "false."

The big picture: Trump's attempts to pressure the Ukrainian president to investigate the Bidens ultimately culminated in his impeachment last year in the Democratic-led House and acquittal in the Republican-led Senate.

What they're saying: "With regard to Ukraine, we had this whole question about whether or not, because [Hunter] was on the board, I later learned, of Burisma, a company, that somehow I had done something wrong," Biden said.

• "Yet every single solitary person when [Trump] was going through his impeachment, testifying under oath who worked for him, said I did my job impeccably. I carried out U.S. policy. Not one single solitary thing was out of line. Not a single thing, number one," he continued.
• "Number two, the guy who got in trouble in Ukraine was this guy, trying to bribe the Ukrainian government to say something negative about me, which they would not do and did not do, because it never, ever, ever happened."

The other side: Biden in turn accused the president of making money from foreign sources, citing a report in the New York Times that Trump has a secret bank account in China. Trump defended himself, saying he was "a businessman doing business" and claiming the account was closed in 2015 before he became president.