As Ukraine underwent dramatic changes in 2014, Vice President Joe Biden played a critical role in the Obama administration's involvement in the revolution that ousted Ukrainian president Viktor Yanukovych.
Following the revolution, Biden would use his influence to help force the creation of the troubled National Anti-Corruption Bureau (NABU). Notably, during the 2016 elections information leaked from NABU on Trump's campaign manager Paul Manafort that helped to create the false narrative that Trump colluded with Russia to win the elections.
Biden would also use the threat of withholding a billion dollars in American loan guarantees to pressure Ukrainian President Petro Poroshenko to fire the prosecutor general. At the time the prosecutor had been investigating Burisma, a Ukrainian natural gas giant that Biden's son, Hunter, was a board member on.
President Donald Trump's personal lawyer, Rudy Giuliani, recently said "keep your eye on Ukraine." In his comments to the Washington Examiner, Giuliani highlighted the "plot to create an investigation of President Trump based on a false charge of conspiracy with the Russians to affect the 2016 elections."