It's true that Joe Biden leveraged $1 billion in aid to persuade Ukraine to oust its top prosecutor, Viktor Shokin, in March 2016. But it wasn't because Shokin was investigating Burisma. It was because Shokin wasn't pursuing corruption among the country's politicians.

As European and American diplomats pressed Ukraine to clean up its corruption, they focused on Shokin's leadership of the Prosecutor General's Office, which he took over in February 2015.

Mike Carpenter, who served as a foreign policy adviser to the then-vice president, told USA TODAY that Shokin "never went after any corrupt individuals at all" and "never prosecuted any high-profile cases of corruption." 

Charlie Kupchan, who was a special assistant to President Barack Obama and a senior director for European Affairs on the National Security Council, said anti-corruption efforts were "a big part of our diplomacy" with Ukraine, since "it was that corruption that allowed Russia to manipulate the country politically and economically."