Trump’s smear campaign comes amidst an impeachment inquiry launched last week, prompted by a telephone conversation between Trump and Ukraine’s president Volodymyr Zelensky that happened in July. A whistleblower recently alerted investigators to the call which Trump, while withholding much-needed military aide to Ukraine, asked Zelinsky to help him drum up dirt on Biden, who is the front-runner to challenge the president for the White House in 2020.