It should be noted that given there is an ongoing Department of Justice investigation into the origins of the Russia investigation, it’s much easier for Trump to defend any reference to that specific investigation as merely making sure that the DOJ gets all the cooperation it needs from a foreign government.
However, several things cut against this benign interpretation. One, the close involvement of Giuliani, Trump’s personal attorney, in the negotiations. Giuliani, you may recall, said in May that the information he was seeking from Ukraine “will be very, very helpful to my client, and may turn out to be helpful to my government.” Two, in the call itself, and in subsequent public statements, Trump has made clear he wants Ukraine to look into both 2016 and the Bidens. Third, while the text exchanges initially involve withholding the White House visit in exchange for an investigation of the 2016 issue, subsequent texts reference “investigations” plural, citing both 2016 and Burisma. Burisma is the company that gave Hunter a $50,000 a month gig while Joe Biden was the Obama administration’s point person on Ukraine. It’s the Biden angle that clearly interests Trump here, which is why in the call he mentions the Bidens by name, but does not mention Burisma by name.
In the aftermath of the call, there are weeks of negotiations over the White House visit. The Trump team wanted a public guarantee in the form of a statement from Zelensky specifying that he would look into the matters. The Ukrainians were clearly trying to pin down dates for a meeting, and Giuliani is clearly pushing for making the statement more explicit. We do not have drafts of the various statements being debated, which would be helpful. However, in an earlier text from July 21, Bill Taylor, Trump’s diplomat based in Ukraine, texts that Zelensky “is sensitive about Ukraine being taken seriously, not merely as an instrument in Washington domestic, reelection politics.” This helps explain the reticence of Ukraine to be overly explicit about a promise to go after the Bidens, which clearly led to differences over the drafting of a statement.